A customer service call center wants to ensure that the majority of

customers$$ calls are answered within a reasonable amount of

waiting time. Based on the customer surveys, the company found

that the waiting time that the customer considers acceptable is up

to a maximum of $40$ seconds. A large sample of current customer

calls was monitored and it was found that the mean and standard

deviation of the waiting time was $31$ second and $4\mathrm{.}5$ seconds

respectively. Calculate the Process capability index and comment

on it$.$ Also determine the percentage calls with waiting time of

more than $38$ seconds