Ok so being relatively new to Differential Equations i am having trouble with this, most likely very simple, problem.

The problem is this: I have a flat object with two strings attached to it, one string is remaining still while the other is moving upwards in the Y direction at a constant, known rate. At what rate will the string that is doing the lifting be moving inwards in the X direction. I believe that this can be solved as a related rates problem but i am having trouble actually solving it.