There is a shrewd boss who uses the following method to determine the selling price of a commodity: Suppose the number of commodities is N, then the selling price of N commodities (unit: yuan) is calculated according to: cost per piece*(1+20%)*N, Make up an integer multiple of 5 (only increase but not decrease), according to this pricing method: 50 yuan for 1 piece; 95 yuan for 2 pieces; 140 yuan for 3 pieces; So how much does this product cost per piece?
有一位精明的老板对某商品用下列办法来确定售价：设商品件数是N，那么N件商品售价(单位：元)按：每件成本*(1+20%)*N算出后，凑成5的整数倍(只增不减)，按这一定价方法得到：1件50元；2件95元；3件140元；4件185元；…，如果每件成本是整元，那么这一商品每件成本是多少元？
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