A 20m ropes passes over a pulley 4m above the ground and a crate on the ground is attached at one end. The other end of the rope is held at a level of 1m above the ground and is drawn away from the pulley. Express the height of the crate over the ground in terms of the distance the person is from directly below the crate. Sketch the graph of distance and height.

I am having a really tough time with this. I have assumed that I need to use the tangent of the angle created to solve this but I am really not finding any solutions that work.