I am not sure about the formula but if you subtract 8,884 from 10,712 you get 1,828. Then, if you divide that by 4 you get 457. 457 fph(feet per hour) should be the climbers vertical speed.
Andrew is wanting to build a slide for his daughter's tree house in the backyard. The tree house is approximately 5 feet off the ground and he wants the slide to have a 30 degree angle with the ground. He will need to by 10 ft of sliding board.