I'm having some difficulty getting a firm grasp on related rates problems. I think I may have solved this particular problem, but I would greatly appreciate it if someone who truly knows what they're doing could give me the "thumbs up" that I indeed did it correctly.

A spotlight on the ground shines on a wall 12 m away. If a man 2 m tall walks from the spotlight toward the building at a speed of 1.6 m/s, how fast is the length of his shadow on the building decreasing when he is 4 m from the building.

The answer I got was -.6 m/s. Am I right? Please tell me I'm right.