A company audit showed that of 875 bills that were sent out, 623 were paid on time, 155 were paid up to 30 days late, 78 were paid between 31 and 90 days late, and 19 were paid after 90 days. One bill is selected at random.

a. What is the probability that the bill was paid on time?

b. What is the probability that the bill was paid late?