(4) A gas-cooled reactor uses helium coolant. The coolant exits the core at 800°C

and flows through a counter-flow heat exchanger where it produces saturated steam

at 7 MPa. The helium leaves the HX at 650°C. Assuming the feedwater temperature

is 200°C, (a) determine the ratio of coolant mass to working fluid mass. (b)

Determine the temperature of the helium at the pinch point.