Air is contained in a vertical piston-cylinder assembly by a piston with a 4-in diameter and a weight of 300 lb,. The atmospheric pressure is 14.7 psia on top of the piston. A total of 4.13 Btu of energy as heat is transferred to the air and the piston rises at constant pressure resulting in a change in volume of 1000 in3. Kinetic and potential energy effects as well as friction between the piston and cylinder wall can be ignored. Determine the change in internal energy, in Btu. (Hint: Watch “Closed System-EB-Volume Change”).