I am not really well adept at these problems and I just don't get where to even start. Please help this poor soul.

56. A paddle wheel has a ten foot diameter. At t = 0, Jenn notices a weed stuck to the top of the paddle, which is eight feet above the surface of the water. It takes 4 seconds for the paddle to return to the same position. Find a function that will model the height of the weed above the water at any time t