Repair calls are handled by one repairman at a photocopy shop. Repair time, including travel time, is exponentially distributed, with a mean of $2\mathrm{.}1$ hours per call. Requests for copier repairs come in at a mean rate of $2\mathrm{.}4$ per eight$-$hour day $($assume Poisson$).$ Determine the following:

a$.$ The average number of customers awaiting repairs