#### Problem 18E

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