An overhead garage door of weight W consists of a uniform rectangular panel AC that is supported

Question:

An overhead garage door of weight W consists of a uniform rectangular panel AC that is supported by two sets of frictionless rollers A and B which slide in horizontal and vertical channels, respectively. The door is held in the position shown by a cable attached to the door at the middle of its upper edge. Express the tension T in the cable in terms of W, a, b, and θ.