A suburban train station has five public telephones, During afternoon rush hours, individuals wanting to place calls arrive at the telephone boots according to a Poisson process, at the rate of 100 per hour. The average duration of a call is 2 min, the actual duration being exponentially distributed.

Determine (a) the expected amount of time an individual must wait for a telephone once having arrived at the booths, (b) the number of people expected to be using or waiting for a telephone.