An Ideal Monatomic Gas Expands Isobarically from State a to State

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 by the gas in expanding isobarically from A to B?

A) 1 × 10³ J
B) 2 × 10³ J
C) 3 × 10³ J
D) 4 × 10³ J
E) 5 × 10³ J