Romeo is chucking pebbles as gently as he can up to Juliet's window as shown in the figure. He is standing at the edge of her rose garden at H = 11.5 m below her window and at D = 5.3 m from the base of the wall. How fast did the pebbles need to go when they left his hand? (note: the pebbles are traveling horizontally when they hit the window).