A 13 m long ladder leans against a wall. The bottom of the ladder is pulled away from the wall at the rate of 6 m/s. How fast does the heigh on the wall decrease when the foot of the ladder is 5 m away from the base of the wall?

A 13 m long ladder leans against a wall. The bottom of the ladder is pulled away from the wall at the rate of 6 m/s. How fast does the heigh on the wall decrease when the foot of the ladder is 5 m away from the base of the wall?