Xiaofang brought 15 yuan to buy pens. The stationery store only has fountain pens of 1 yuan each and pencils of 0.6 yuan each. How to buy.
小芳带了15元钱去买笔，文具店只有每支1元的水笔和每支0.6元的铅笔，如果要把钱全部用完，而且不能只买一种笔，她有多少种不同的购买方法．
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