A closed feedwater heater in a regenerative steam power cycle heats 40 lbm/s of water from 200

Question:

A closed feedwater heater in a regenerative steam power cycle heats 40 lbm/s of water from 200 F, 2000 lbf/in.2 to 450 F, 2000 lbf/in 2, the extraction steam from the turbine enters the heater at 500 lbf/in 2, 550 F and leaves as saturated liquid. What is the required mass flow rate of the extraction steam?