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(15choose0)*.2^0*.8^15+(15choose1)*.2^1*.8^14+(15choose2)*.2^2*.8^13+(15choose3)*.2^3*.8^12
(15choose0)*.2^0*.8^15+(15choose1)*.2^1*.8^14+(15choose2)*.2^2*.8^13+(15choose3)*.2^3*.8^12
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