The Leaning Tower of Provlle creates an 85 degree angle between itself and the level ground around the tower. The tower's shadow is 100 feet long. If it can be determined, which of the following expressions gives the distance, in feet, from the top of the tower to the ground?

Turns out it can't be determined but is this because 100 cot 85 = x and so x = 8ft and an 8ft building can't cast a 100ft shadow or is there some other reason??