This is the boss. No calculator. Tonight $i = 10\%$ throughout, and the two factors you need are handed to you pre-rounded — (P/F, 10%, 5) and (A/P, 10%, n) — so every line is a multiplication you can do on the page. Everything is chosen to fit in your head.

Two bids, six lines, and every answer feeds the next: the year-5 rebuild discounted back, the rebuild added to the first cost, the total annualised, the running cost added, the rival bid priced the same way, and then a payback cross-check on the extra capital. Write each line down as you go — one slip at the top rolls all the way to the recommendation.

Note what the last line actually asks. It does not want another number; it wants a decision, with your name on it. The arithmetic exists only to earn you the right to make it. Watch for the trap this chapter has been building toward: the bid that is cheaper to buy is not the bid that is cheaper to own, and the gap between those two sentences is where the money in this subject lives.

Everything in the chapter rides in this one evaluation. 5★ under par here is the chapter crown. Clock in.