Martin Coleman, credit manager for Beck's, knows that the company uses three methods to encourage collection of delinquent accounts. From past collection records, he learns that

70 percent of the accounts are called on personally, 20 percent are phoned, and 10 percent are sent a letter. The probabilities of collecting an overdue amount from an account with the three methods are 0.75, 0.60, and 0.65 respectively. Mr. Coleman has just received payment from a past-due account. What is the probability that this account

(a) Was called on personally?

(b) Received a phone call?

(c) Received a letter?