Correct answer: 560 J
The change in internal energy (ΔU) for the entire process AC can be calculated using the first law of thermodynamics: ΔU = Q - W. The heat added (Q) in the entire process AC is the sum of heat added in AB and BC, i.e., Q = 600 J + 200 J = 800 J. The work done (W) is the area under the PV curve, which is the work done in AB (W_AB = PΔV = 3 × 10⁴ × (5 × 10⁻³ - 2 × 10⁻³) = 90 J) plus the work done in BC (W_BC = 0, as volume is constant). Thus, W = 90 J. Therefore, ΔU = 800 J - 90 J = 560 J.