12 pounds of working fluid is moving with a velocity of 70 ft/sec through a process. As it moves from state point 1 to state point 2 its elevation increases 80 ft, it delivers 9000 ftlbf of work, and it receives 70 Btu of heat. During this movement the pressure and density of the fluid do not change. Determine the change in internal energy of the working fluid (Btu/lbm).