A power plant operates on a regenerative vapor power cycle with one open feedwater heater. Steam enters the first turbine stage at 12 MPa, 560°C and expands to 1 MPa, where some of the steam is extracted and diverted to the open feedwater heater operating at 1 MPa. The remaining steam expands through the second turbine stage to the condenser pressure of 6 kPa. Saturated liquid exits the open feedwater heater at 1 MPa, with saturated liquid condensate exiting and being throttled into the open feedwater heater. The feedwater leaves the closed heater at 12 MPa, 170°C. Steam is extracted between the second and third turbine stages at 0.15 MPa and fed into an open feedwater heater operating at that pressure. Saturated liquid at 0.15 MPa leaves the open feedwater heater. Assume isentropic processes in the pumps and turbines. If the net power developed by the cycle is 320 MW, determine:

a. The rate of heat input to the steam passing through the steam generator, in MW.
b. The thermal efficiency.
c. The mass flow rate of steam, in kg/h, into the first turbine stage.
d. Sketch the process on T-s coordinates.