The total work done per cycle is W c y c l e = p A ( v 2 − − v 1 ) + p C ( v 4 − − v 3 ) = p A ( v 2 − − v 1 ) + p C ( v 1 − − v 2 ) = ( p A − − p C ) ( v 2 − − v 1 ) , which is just the area of the rectangle. If the total heat flow per cycle is required, this is easily obtained. Since Δ Δ U c y c l e = Q c y c l e − − W c y c l e = 0 , we have Q c y c l e = W c y c l e .