Mom gives Xiao Ming 30 yuan to buy cups. It is known that each big cup is 3 yuan, and each small cup is 2 yuan. If the money is used up, how many different ways are there in total?
妈妈给小明30元钱去买杯子，已知大杯子每只3元，小杯子每只2元，如果把钱正好用完，那么一共有多少种种不同的购买方法？
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