First find the total volume of the Mountain Dew: 6 cans * 12 oz/can = <<6*12=72>>72 oz
Then find the total volume of the punch: 72 oz + 28 oz + 40 oz = <<72+28+40=140>>140 oz
Then divide the total volume by the volume of each serving to find the number of servings: 140 oz / 10 oz/serving = <<140/10=14>>14 servings
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