Question $2$: On a typical day, the average arrival rate of customers to the Stonebriar Mall is $225$ per hour. Suppose each customer stays in the mall for an average of $135$ minutes.

$1.$ What is the average number of customers in the mall at any time?

A third of all the customers come alone and make up$,$ on average, $20\%$ of the customers in the mall. The remaining customers come to mall with their families.

$2.$ How long, on average, does a single customer $($those who come alone$)$ spend in the mall?

$3.$ Estimate the average time a typical family spends in the mall