Repeat Prob. 9-72E if the engine is to be operated to produce 2.5 Btu of work for the same external heat input?

Prob. 9-72E:

An ideal Stirling cycle filled with air uses a 75°F energy reservoir as a sink. The engine is designed so that the maximum air volume is 0.5 ft³ , the minimum air volume is 0.06 ft³ , and the minimum pressure is 15 psia. 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 engine. Determine the temperature of the energy source, the amount of air contained in the engine, and the maximum air pressure during the cycle.