AP Physics C rotational motion?

Maybe you don't need to calculate the torque. Since gravity always works vertically downwards, the leverage is the horizontal distance from the weight to the fulcrum. At any angle theta from the vertical, the horizontal distance is equal to sine theta times the length of the lever. So since a (more experienced) plumber would know that he gets best advantage when the wrench handle is horizontal, and since the istant has got the handle at 45 degrees, he's only got half the leverage, so he would need to be twice as heavy!