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Below you'll find a few helpers along the way to properly sizing your wire or cable. As we are primarilly marine focused we have added some tables regarding the amperages as suggested by the ABYC for the marine environment. These standards might be a bit more strict then those in the automotive environment however, they err on the side of caution and were developed with safety in mind.
The volatge drop calculator will allow you to find the percentage of voltage drop as well as the current delivered at the end of the wire run. In the boating world it is suggested:
3% max voltage drop for conductors providing power to panels and switchboards, navigation lighting, bilge blowers, main DC feeders, and any other circuit where voltage drop should be kept to a minimum
10% max voltage drop on conductors used for general lighting and other non-critical circuits
The ampacity (amperage) tables on the left side help to choose the correct size cable to handle the power load for which you are trying to find the correct wiring. There are individual tables for single conductor and multiple conductor runs as current carrying conductors which are bundled together will transfer heat to each other in effect reducing their safe current handling capabilities
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Allowable amperage of single conductors rated 105C
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Size
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Sq
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AWG
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SAE
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Ampacity Outside / Inside of Engine Space
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AWG
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mm
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CM area
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CM area
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Outside
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Inside
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18
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0.8
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1,600
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1,537
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20
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17
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|
16
|
1
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2,600
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2,336
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25
|
21
|
|
14
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2
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4,100
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3,702
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35
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30
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|
12
|
3
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6,500
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5,833
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45
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38
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|
10
|
5
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10,500
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9,343
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60
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51
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8
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8
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16,800
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14,810
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80
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68
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|
6
|
13
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26,600
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24,538
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120
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102
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4
|
21
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42,000
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37,360
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160
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136
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2
|
34
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66,500
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62,450
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210
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178
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|
1
|
42
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83,690
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77,790
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245
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208
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1/0
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53
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105,600
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98,980
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285
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242
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2/0
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68
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133,100
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125,100
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330
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280
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4/0
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107
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211,600
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205,500
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445
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378
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Allowable amperage of conductors when multiple conductors
are bundled together for cables rated 105C
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Size
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2 conductors
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3 conductors
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4-6 conductors
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7-24 conductors
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AWG
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Sq.mm
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Outside Engine Space
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Inside Engine Space
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Outside Engine Space
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Inside Engine Space
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Outside Engine Space
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Inside Engine Space
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Outside Engine Space
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Inside Engine Space
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18
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0.8
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20
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17.0
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14.0
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11.9
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12.0
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10.2
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10.0
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8.5
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16
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1
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25
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21.3
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17.5
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14.9
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15.0
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12.8
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12.5
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10.6
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14
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2
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35
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29.8
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24.5
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20.8
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21.0
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17.9
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17.5
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14.9
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12
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3
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45
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38.3
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31.5
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26.8
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27.0
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23.0
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22.5
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19.1
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10
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5
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60
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51.0
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42.0
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35.7
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36.0
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30.6
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30.0
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25.5
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8
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8
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80
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68.0
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56.0
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47.6
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48.0
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40.8
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40.0
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34.0
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6
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13
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120
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102.0
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84.0
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71.4
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72.0
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61.2
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60.0
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51.0
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4
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21
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160
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136.0
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112.0
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95.2
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96.0
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81.6
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80.0
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68.0
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2
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34
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210
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178.5
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147.0
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125.0
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126.0
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107.1
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105.0
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89.3
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1
|
42
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245
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208.3
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171.5
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145.8
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147.0
|
125
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122.5
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104.1
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1/0
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53
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285
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242.3
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199.5
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169.6
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171.0
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145.4
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142.5
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121.1
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2/0
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68
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330
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280.5
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231.0
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196.4
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198.0
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168.3
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165.0
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140.3
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4/0
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107
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445
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378.3
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311.5
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264.8
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267.0
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227.0
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222.5
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189.1
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