An ideal gas follows the process shown in the PV diagram below.  The gas absorbs 960 J of heat to triple its pressure during the process. What is the relationship of internal energy at point X to internal energy at point Y. Explain your reasoning.

• A. U_Y < U_X, Work done decreases internal energy.
• B. U_Y = U_X, Heat absorbed is used to do work.
• C. U_Y > U_X, Higher pressure means greater internal energy.
• D. U_Y - U_X < 960 J; Heat absorbed is shared between work and internal energy.
• E. U_Y - U_X = 960 J; ΔU is equal to the heat absorbed by the gas.

Answer: (E)