Question

A rock is projected from the edge of the top of a building with an initial velocity of 19.6 m/s at an angle of 31 degrees above the horizontal. The rock strikes the ground a horizontal distance of 77 m from the base of the building. The acceleration of gravity is 9.8 m/s^2.(squared) Assume: The ground is level and that the side of the building is vertical. Neglect air friction. How tall is the building?