There are cases when this is the answer, e.g. when the board is square-shaped, and Marie is determined to always saw at the shortest possible horizontal/vertical line. Nobody said the pieces should be exactly the same size.
In fact nobody told anything about anything. What a shitty, vaguely written exercise.
Oh, wait. Then it would take 17,5 minutes to saw it into 4 pieces. Um... Let's say Marie likes to think outside the box and saw things not according to any rules.