Problem $3$ Isothermic Engine

Consider the heat engine shown $($process is clockwise$).$ The isothermic process does a magnitude of work $P_0{V}_0.$ The values shown on the plot are known. $($a$)$ Find the volume at position $1.($b$)$ Find the total work done on the environment. $($c$)$ Find the heat during each phase. Note which contribute to $Q_H$ and which contribute to $Q_C.($e$)$ Find the efficiency of the heat engine. $($e$)$ What would be the maximum possible efficiency of the engine that would still satisfy the second law of thermodynamics?