An ideal Stirling cycle filled with air uses a 75 F energy reservoir as a sink. The engine is designed to so that the maximum air volume is 0.5 ft3 , the minimum air volume is 0.05 ft3 , and the minimum pressure is 15 psi. It is to be operated such that the engine produces 2 Btu of net work when 5 Btu of heat are transferred externally to the to the engine. Determine the temperature of the energy source, the amount of air contained inside the engine, and the maximum air pressure during the cycle.