Phone Calls In the month preceding the creation of this exercise, the author made 18 phone calls in 30 days. No calls were made on 17 days, 1 call was made on 8 days, and 2 calls were made on 5 days.

a. Find the mean number of calls per day.

b. Use the Poisson distribution to find the probability of no calls in a day.

c. Based on the probability in part (b), how many of the 30 days are expected to have no calls?

d. There were actually 17 days with no calls. How does this actual result compare to the expected value from part (c)?