You can put this solution on YOUR website! Maybe. How tall is the doorway? The doorway would be expected to be bigger in tallness than in its width, but it might not need to be. The middle path that the table top must fit would be a diagonal of the doorway ------- Pythagorean Triangle-Theorem.
If y is the tallness of the doorway, and width of the doorway is 2.5 meters, then setup , which turns the question into, how tall should the doorway be so that the tabletop will fit?