An ideal monatomic gas expands isobarically from state A to state B. It is then compressed isothermally from state B to state C and finally cooled at constant volume until it returns to its initial state A. How much work is done on the gas in going from B to C?

Question

An ideal monatomic gas expands isobarically from state A to state B. It is then compressed isothermally from state B to state C and finally cooled at constant volume until it returns to its initial state A. How much work is done on the gas in going from B to C? 
Va=4x10^-3
Vb=8x10^-3
Pa=Pb=1x10^6
Pc=2x10^6
Ta=600K
Tb=1200K (determined in a previous question)