Figure shows a torch producting a straight light beam falling on a plane mirror at an

Figure shows a torch producting a straight light beam falling on a plane mirror at an angle `60^(@)` The reflected beam makes a spot P on the screen along y-axis . If at t=0, mirror starts ratating about the hinge A with an angular velocity `(omega)=1^(@)` per second clockwise. Find the speed of the spot on screen after time t = 15 s