Problem $4)$ A clamshells will be digging a basement as shown in below assume depth was $3m,$ estimate the production of medium$-$weight clamshell excavating hard clay, the heaped bucket capacity is $0\mathrm{.}85cm,$ and the cycle time is $20s$ and job efficiency is $50mi\frac{n}{h}r.$ Equipment costs are $100$ SR per operation hour.

A$)$ Estimate the time required to perform the excavation?

B$)$ What is the cost per bank cubic meter of excavation and total cost?