A regenerative vapor power cycle has two turbine stages with steam entering the first stage at 2000psia and 900F and expanding to 100psia. Some of the flow is extracted at 100psia and directed to a closed feedwater heater, where it is condensed to a saturated liquid at 100psia before being trapped into the condenser. The feedwater leaves the closed heater at 2000psia and 450F. The condenser pressure is 1psia. After determining that the turbine stages and pumps operate isentropically, determine the thermal efficiency of the cycle.