I was wondering if someone could just check my answer on this one.

A laser is pointed horizontally at a wall that stretches on to infinity perpendicular to the path of the laser. The angle of the laser in relation to the wall changes at a constant rate, R. The distance between the laser and the wall is D. Assuming the light travels instantaneously what is the apparent acceleration of the dot the laser makes on the wall as a function of time?

I got: