please use thermodynamic principles

A Rankine cycle with superheat and re-heat runs with a mass flow rate of 7kg/s, a low pressure of 70 kPa (P1), a high pressure of 12MPa(P2), and a middle pressure of 3MPa(P4). Steam exits both the superheater and the reheater with a temperature of 900C. Assume the pump is isentropic and each of the turbines has an isentropic efficiency of 90%. a) Draw a T-s diagram of the process. b) What is the net power output of the cycle? c) What is the thermodynamic efficiency of the cycle? (Solution: Wnet=12.87MW,th=40.2% )