10 coupons are given to 20 shoppers in a store. Each shopper can receive at most one coupon. 5 of the shoppers are women and 15 of the shoppers are men. a. If the coupons are identical, how many different ways are there to distribute the coupons so that at least one woman receives a coupon? b. If the coupons are different, how many different ways are there to distribute the coupons so that at least one woman receives a coupon?