As you can see, the diagonal actually creates a right triangle. Not only that, but you’re given two legs. Therefore, you can use the Pythagorean theorem to find the distance. Specifically, 78 (73?) feet and 27 feet.
Plug in for “a” and “b” to find your distance in:
a^2 + b^2 = c^2
sqrt(a^2 + b^2) = c
Plug in and solve