68. With reference to the chart, if a boiler generates saturated steam at 385.3 psig, how much heat per pound was required to change the water into steam if the feedwater temperature was initially 220°F

The heat required to convert feedwater to saturated steam is the difference between the saturated steam enthalpy (1204.5 BTU/lb at 400 psia) and the feedwater enthalpy (188.1 BTU/lb at 220F), resulting in 1016.4 BTU/lb.