You tell two friends about a website they can go to in order to receive coupons to a popular clothing store. the next day, each of them tells 2 more friends, and the next day, each of those friends tells 2 more friends. so the first day, 2 new people know about the coupons; the second day, 4 new people know about the coupons; the third day, 8 new people know about the coupons, etc. how many people find out about the coupons on the ninth day?