A solar-driven Rankine-cycle power plant uses refrigerant R-134a as the working fluid. During operation (i.e., daytime), the turbine inlet state is 220 F and 200 psia. The air-cooled condenser operates at a pressure of 80 psia. The pump and turbine isentropic efficiencies are 0.70 and 0.80, respectively. The work output is 100 hp when the solar-collector input is 200 Btu/hr·ft². The R-134a leaves the condenser as saturated liquid. 

Determine

(a) The thermal efficiency

(b) The refrigerant mass flow rate (klb_m/hr)

(c) The required collector surface area (ft²).