Please solve letter A at the bottom. All breakpoints are exactly located at grid nodes

The two lateral, highest points $($bank$-$floodplain breakpoints$)$ are at the same elevation

Bankfull width is $16m$

Bankfuil depth is $6m$

The two middle points $($channel bed$)$ are strictly below floodplain, and at different elevations

a$.)$ Derive mathematical expressions for $A(y),b(y).$ and $P(y),$ for $y$ ranging from $0$ to bankfull depth.