. In Exercise 64, consider the following additional information on credit card usage:
70% of all regular fill-up customers use a credit card.
50% of all regular non-fill-up customers use a credit card.
60% of all mid-grade fill-up customers use a credit card.
50% of all mid-grade non-fill-up customers use a credit card.
50% of all premium fill-up customers use a credit card.
40% of all premium non-fill-up customers use a credit card.
Compute the probability of each of the following events for the next customer to arrive (a tree
diagram might help).
(a) {mid-grade and fill-up and credit card}
(b) {premium and non-fill-up and credit card}
(c) {premium and credit card}
(d) {fill-up and credit card}
(e) {credit card}
(f) If the next customer uses a credit card, what is the probability that s/he purchased premium
gasoline?