Exercise 3 - solution

Planted March 2027:
- First flowers: 3 to 4 years later, so roughly 2030 to 2031.
- First useful harvest: around 5 years later, so about 2032. (Full maturity for arabica takes about 7 years, so about 2034.)

Why replacing plants is slow: a new plant takes about five years to give a useful crop, so replanting means years without income from that field. That makes farms reluctant to replace plants quickly, even when a disease such as leaf rust arrives. (The waiting-time part comes from the article; the farm-economics reasoning is the exercise's own inference.)