Customers at a Publix grocery store in Charleston, South Carolina, can pay for purchases with cash, a debit card, or a credit card. Fifty-five percent of all customers use cash and 38% use a debit card. Careful research has shown of those paying with cash, 75% use coupons; of those using a debit card, 35% use coupons; and of those using a credit card, only 10% use coupons. Suppose a customer is randomly selected.
a. What is the probability that the customer pays with a credit card and does not use coupons?
b. What is the probability that the customer does not use coupons?
c. If the customer does not use coupons, what is the probability that he paid with a debit card?