Problem $1.$ A four$-$lane freeway $(2$ lanes each direction$)$ is located on level terrain and has a design speed of $70mph,12-$foot lanes, and no lateral obstructions within $8$ feet of pavement edges. The traffic stream consists of cars and trucks only $($no buses or recreational vehicles$).$ A weekday peak hour volume of $1800$ vehicles is observed, with $500$ arriving in the most congested $15-$minute period. If a level of service no worse than $C$ is desired, determine the maximum number of trucks that can be present in the peak hour traffic volume.