Steve bought $25 worth of groceries. He bought a gallon of milk for $3, two boxes of cereal for $3.5 each, 4 bananas for $.25 each, four apples that cost $.5 each and a number of boxes of cookies. The cookies cost twice as much per box as the gallon of milk. How many boxes of cookies did he get?
Please reason step by step, and put your final answer within \boxed{}.
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