Mate in 5 Exercise 15

White plays and wins in 4 moves https://lichess.org/4FgOThC9

1. Kc6 Ka8 2. Kb6 Kb8 3. Na6+ Ka8 4. Bc6#

The analysis board does checkmate in 5 moves

1. Kc6 Ka7 2. Kc7 Ka8 3. Kb6 Kb8 4. Na6+ Ka8 5. Bc6#

Source:

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