This is the boss. No calculator — the barometer reads a round 100 kPa, water costs a round 4 kJ/(kg·K), and steam a round 2250 kJ/kg. Those are the numbers an operator keeps in their head for a site sanity check, and every draw here is chosen to fit in yours.

Two rigs, and every answer feeds the next. The receiver first: convert the datum, ride the pressure up with the temperature, convert the datum back, then decide. The deaerator second: sensible heat to the boil, latent heat for the flash, and the two totals never mix. Write each line down as you go, because one early slip rolls all the way to the floor.

And note what the receiver's last line actually asks. It does not want another number; it wants a decision — does the valve lift — the way a real check does. The arithmetic is only there to earn you the right to make it. Remember which datum a relief valve is set in before you answer.

Everything in the chapter rides in these two rigs. 5★ under par here is the chapter crown. Clock in.