What is the change in internal energy of the system?

Question

Refer to the data presented in the accompanying pressure-versus-volume graph. When a system changes from A to B along the path shown, it gains 2890 J of heat. What is the change in internal energy of the system?

http://edugen.wiley.com/edugen/courses/crs1507/art/qb/qu/c15/ch15p_14.gif

Answer 1

The change of internal energy is the sum of work done at the system W plus heat transferred Q:
ΔU = W + Q

where the work is
W = - ∫ p dV
In the sketch you have only two types of changes:
- vertical path
p changes and V is constant. Thus the work for this sections equals zero
- horizontal path
V changes and p is constant. Thus the work for this sections is W = - p · ΔV

Therefore
W = - 10·10⁴ Pa · 12·10⁻³ m³ - 15 · 10 ⁴ Pa · 12·10⁻³ m³
= -3000J
and

ΔU = -3000J + 2890J = -110J

Answer 2

That link takes me to the Wiley Plus log in page. It doesn't show the graph.