A hardware store determines that 70% of its customers do not use the self-checkout system to make their purchases. It also determines that 80% of its customers pay by credit card. Among those using the self-checkout system, however, only 60% pay by credit card.

(a) Use this information to determine the probability that a customer uses the self-checkout system and pays by credit card.

(b) If use of the self-checkout system and payment by credit card are independent, what would the probability in part (a) be?