2. A closed system with a mass of 15 Ibm is pulled up a rough inclined slope. 8 Ibf is applied to raise the system and overcome friction while the system traverses 3 ft along the surface. During this process, the system loses 0.3 Btu by a combination of radiation and convection and an electric resistance heater inside the system draws 0.25 KW of electricity over 2 s. At the start of the process the system has a velocity of 7 ft/s and an elevation of 6 it above the ground. At the end of the process the system has a velocity of 1 ft/s, an elevation of 8 ft and an internal energy of 4 Btu. Find the internal energy at state 1, in Btu