This is the boss. No calculator — today $g = 10\ \mathrm{N/kg}$, the round number every engineer keeps for mental work and site sanity checks, and the depths have been chosen so that $2gh$ is a perfect square and the root comes out whole. One standpipe, one long problem, and every answer feeds the next: the depth becomes a pressure, the depth becomes a jet speed, the jet speed and the outlet become a discharge, and the discharge faces the duty on the schedule. Write each line down as you go — one early slip runs all the way to the bottom.

Note what the last line actually asks for. It does not want another number; it wants a decision, the way a real check does. Pump or no pump. The arithmetic is only there to earn you the right to make it.

Everything in the chapter rides in this one tank: hydrostatic pressure, the pressure–head bridge, Torricelli's trade of height for speed, and Q = Av at the outlet. 5★ under par here is the chapter crown. Clock in.