An Ideal Monatomic Gas Expands Isothermally from State a to State

Multiple Choice

An ideal monatomic gas expands isothermally from state A to state B. The gas then cools at constant volume to state C. The gas is then compressed isobarically to D before it is heated until it returns to state A.
-What is the internal energy of the gas at point B?

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