Background. You are excavating a $100$ ft long $4ft$ wide x$10$ ft deep utility trench. The soil is a cohesive silty loam with an unconfined compressive strength qu $=2$ ksf$.$ You plan to use shoring constructed of upright sheeting and hydraulic bracing as shown. The hydrautic cylinders are $5$ feet apart horizontally. Your company already owns the shoring material. You estimate that it will cost $$225$ in labor to install it

a$.$ What volume of excavation is required for the shored solution?

b$.$ What volume of excavation is required for the sloped solution?

c$.$ The cost for excavation, backfill and compaction is $$\frac{2\mathrm{.}50}{?}$ bcy: Is it cheaper to install shoring or to slope the excavation $($disregard time impacts$)?$