$[20$ Marks$]$ Thermodynamic cycles for two different reversible engines, i$.$e$.,$ engine $A($square$)$ and engine B $($triangle$),$ are shown in the figure. The cycles are drawn to the same scale, and the engines work as closed systems. Show all your steps and justify any assumptions.

A$.$ Find the net work output of engine A and engine $B.[10$ marks$]$

B$.$ Find the efficiency of engine A and engine B$.[10$ marks$]$