Avis Company is a car rental company that is located three miles from the Los Angeles airport $($LAX$).$ Avis is dispatching a bus from its offices to the airport every $2$ minutes. The average traveling time $($round trip$)$ is $20$ minutes.

a$.$ How many Avis busess are traveling to and from the airport?

b$.$ The branch managerwantss to improve the service and suggests dispatching buse every $0\mathrm{.}5$ minutes. she argues that this will reduce the average traveling time from the airport to the Avis offices to $2\mathrm{.}5$ minutes. Is she correct? If your answer is negative, what will the average traveling time be $?$