You don't even need a calculator for this one.40 degrees is less than 45 degrees, and 45 degrees is the angle of elevation where the height would be _equal to_ the distance from the base. The choice that's less than 100 is d.More generally, the formula for the height of the building would be...h = d * tan ewhere...h is the height.d is the distance you are from the base of the building.e is the angle of elevation to the top of the building.
