I'm replacing my old bathroom fan with a new fan/light combo. The new fan/light has four(4) wires, but the existing switch has only three(3) wires. How do I wire this set-up? There are white, blue, and black wires on the fan/light, and what I guess is a screw for the ground wire. But the existing switch wires are white, black, and a bare copper wire. I really want the fan and light to come on with a single switch if possible. Is this even possible?