I like you books but there is an error in MREXCEL 2021 and likely in your other books if you use the same example. On pages 208-11, you use the staff scheduling problem found in SOLSAMP. It is incorrectly formulated. The constraint for Friday, Saturday should be 1 1 1 1 1 0 0, not 1 1 1 1 1 0 1. Microsoft has been notified of this many times but has never corrected it.
Steve
Steve