3. Three brothers need to move a piano weighing 250 kg, a sofa weighing 100 kg, and more than 100 boxes each weighing 50 kg from one apartment to another. A small van with a driver has been hired for 5 trips there (and 4 back), which can carry 500 kg of cargo and one passenger at a time. The brothers can load or unload the sofa with two of them, the piano with all three, and any of the brothers can handle the boxes alone. They need to move all the furniture and as many boxes as possible. What is the maximum number of boxes they can move? (The driver does not load, there is no other transport or helpers, and passengers cannot be carried instead of cargo).


- Answer: 33 boxes. Example. Sequence of flights: