A manufacturer of coffee enclosed a premium coupon with each $2.50 (at whole sale) jar of coffee that it sold to retailers. Customers could use this coupon to apply to $0.50 of the price of a new type of instant tea that the manufacturer was introducing and that sold for $2.00 wholesale. The manufacturer reimbursed retail stores $0.60 for each such coupon they submitted. (The extra $0.10 was to pay the grocer for coupon handling costs.) Past experience with similar premium offers indicated that approximately 20 percent of such coupons are eventually redeemed. At the end of 1997, however, only about 10 percent of the coupons issued in 1997 had been redeemed. In recording the revenues for the company for 1997, what allowance, if any, should be made for these coupons? Why? If an allowance should be made, should it apply to the sales revenue of coffee or to the sales revenue of tea? Why?

最后两个allowance应该怎么理解？

为什么我手上的中文版说是销售折扣？优惠券明明是商业折扣啊！

求大神……