Numerical answer type, answer in J, tolerance 1.
Answer: 1077 J
A to B: wby=RTln3=2740.2 J. At C, V is one third of that at B at the same pressure, so TC=100 K; B to C: wby=PΔV=R(TC−TB)=−1662.8 J. C to A is isochoric, work 0. Net =2740.2−1662.8=1077.4 J, about 1077 J.