Problem $6-8($Algo$)$

Safety regulations require that the time between airplane takeoffs $($on the same runway$)$ will be at least $2$ minutes. When taking off, the run time of an airplane on the runway is $42$ seconds. Planes are on average waiting $3$ minutes and $42$ seconds for takeoff. On average there are $15$ planes taking off per hour. How many planes are either on the runway or waiting to take off?

Note: Round your answer to $2$ decimal places.

Number of airplanes