Problem: A sign of height h is to be placed on top of a building. The ideal height of the sign would maximize the angle between the obervers line of vision and the top-to-bottom of the sign.

Known: The building is 50 feet tall.

The walkway is 60 feet from the building.

The observer is 5 feet tall.

Edit: After taking another look at the problem, it seems that the angle that it wants to be a max when the walkway is 60 feet from the building is the angle between the observers view of the top of the sign to the observers view to the bottom of the sign.