You want to choose any 2 of the 4 measurements
which would be C(4,2) = 6
- easy to list
If the order of the dimensions matter, there would be 12 of them.
e.g. in a 10 by 12, you could have the door along the 10 ft side or the
12 ft side, they would be "different" sheds
You will have to decide how to interpret the question.