Between 35 and 51.if we assume a reasonable stacking technique for stability, every box not on top can be supported on 3 sides at 40.

We also don’t know that every box is the same size. With that format screw it could be as low as 21.

This is why mechanical diagrams include an isometric view and xray lines.

Edit: I see now it specifies cubes, so the number couldn’t be 21, but it could still be less than 35. I’m not figuring that one out.

Also why can’t you see the trailer in the top view when it protrudes on the sides?