Afitness center runs a contest for customers who enroll in its annual membership plan. the customers are allowed to draw a coupon from a jar that contains 20 coupons for 1 month of extended membership, 10 coupons for 1.5 months of extended membership, and 5 coupons for 2 months of extended membership. assuming a month has 30 days, if the expected value of extended membership (in days) on the first draw is given by the expression a + b + c, identify the correct numerical expressions for a, b, and c.