Hi, I need help with this Calculus question. It's asked derivative, or the rate of change of the man's shadow changing on the building when he is 14m from the building.

BONUS 1%: Must be handed in by 8:30 a.m. the following day. A light is on the ground 20m from a building. A man 2 m tall walks from the light directly toward the building at 1 m/s. How fast us the length of his shadow on the building changing when he is 14 m from the building