This is the boss. No calculator — 120 V and whole ohms, chosen to fit in your head, the way a well-set final always is. One circuit traced end to end: the series total, the current, the power, the evening's energy in kilowatt-hours, and the breaker's verdict. Every answer feeds the next — write each one down, with its units.

Everything from the chapter rides in it — the ohms that stack, the face of power that fits the givens, the ×3.6 world of the meter. 5★ under par here is the chapter crown. Throw the switch.