Answer:
the answer is 3×3×5×5×17=3825 use prime factorization
I am guessing it is b! because BG and BA are sides, and BAU and BGN are angles.
9 feet? Not sure lmk if I'm wrong other people answering

which follows from the usual change of coordinates via

and Jacobian determinant

Swap the order, so that the integral is

and now let

, so that

. Now, you have