Mate in 5 Exercise 21

Black plays and wins in 3 moves https://lichess.org/P30zjIkZ/black

1... Kg6 2. Ra8 Kf7 3. Ra1 Rh6#

The analysis board does checkmate in 5 moves

1... Rf7 2. Rb6+ Ng6+ 3. Rxg6+ Kxg6 4. Kg8 Rf1 5. Kh8 Rf8#

Source:

https://www.amazon.com/Chess-Puzzles-Advanced-Expert-Level/dp/B0917YQZP1