This is the boss. No calculator — the values are chosen to fit in your head: 5% of round numbers, and powers of 1.1 you can build one year at a time ($1.1^{2} = 1.21$). Keep the Rule of 72 in your pocket: money at $r\%$ doubles in about $72/r$ years — at 10%, call it seven — the instant sanity check on any compound claim anyone ever makes you.

One signing bonus, three plans, and every answer feeds the next: simple interest, then compound, then the split deposits, then the podium. Write each line down as you go. 5★ under par here is the chapter crown. Clock in.