Solve this problem please step by step. In the below pictured excavated earth channel, the triangular sides are constructed of

rubble masonry and the rectangular sides are of finished concrete.

a$.$ Given a change in elevation of $6m$ over $2km,$ calculate the flowrate in the channel

assuming that it is full to the top.

b$.$ Find the depth required in the channel for the flow to be at $80\%$ of maximum $($full$)$

flow.