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QUESTION $13$

$M{M}^2$ has a queuing problem where customers who line up to pay their selections form the waiting line. The $M{M}^2$ system consists of an arrival rate of $12$ per hour according to a Poisson distribution, and service times are on average equal to $4$ minutes per customer.

What is the number of customers waiting in the queue on average?

a$.3\mathrm{.}2$

b$.0\mathrm{.}152$

c$.4\mathrm{.}0$

d$.0\mathrm{.}333$

e$.0\mathrm{.}952$