$17\mathrm{.}6-2.*$ The $4$M Company has a single turret lathe as a key work center on its factory floor. Jobs arrive at this work center accord ing to a Poisson process at a mean rate of $2$ per day. The process ing time to perform each job has an exponential distribution with a mean of $14$ day. Because the jobs are bulky, those not being worked on are currently being stored in a room some distance from the machine. However, to save time in fetching the jobs, the produc tion manager is proposing to add enough in$-$process storage space next to the turret lathe to accommodate $3$ jobs in addition to the one being processed. $($Excess jobs will continue to be stored tem porarily in the distant room.$)$ Under this proposal, what proportion of the time will this storage space next to the turret lathe be ade quate to accommodate all waiting jobs? $($a$)$ Use available formulas to calculate your answer.