Question: For a particular kind of call, the phone company charges $1 for the first minute of any portion thereof, and one cent per second for time after the first minute. Calculate the approximate value of the long-run average charge per call assuming the distribution of call duration is:
a) exponential with mean 1 minute:
b) exponential with mean 2 minutes:
c) gamma with shape parameter 2 and mean 1 minute.