A utility contractor is to install the sewer line whose plan and profile are given. The trench is to have the cross section shown in the figure.

a$)$ Using the average$-$end method, determine the total volume of excavation in cubic yards needed to install the sewer line. Neglect the excavation of the manholes. Answer $q,/$d ${?}^3$

b$)$ The pipe is surrounded by gravel. The depth of the gravel is $2$ ft $.$ The outside diameter of the sewer pipe is $13$ inches. Determine the quantity of gravel needed for the sewer line. Answer $\frac{?}{d^3}$

c$)$ Determine the volume of backfill for the sewer line. Answer $q,y{d}^3$