In a System Composed of Nitrogen Gas in a Cylinder $\Delta$

In a system composed of nitrogen gas in a cylinder fitted with a piston,when 2.00 kJ of energy is transferred as heat at an external pressure of 2.00 atm,the nitrogen gas expands from 2.00 to 5.00 L against this constant pressure.What is $\Delta$ U for the process?

A) (-0.608 kJ)
B) +1.39 kJ
C) +2.61 kJ
D) 0
E) (-2.61 kJ)