Mathematics Integration Level: Misc Level

The top of a ladder 6 meters long is resting against a vertical wall. Suddenly, the ladder begins to slide downwards. At the instant when the foot of the ladder is 4 meters from the wall, it is sliding away at the rate of 0.5 m/sec. How fast is the top sliding downwards at this moment? How far is the foot from the wall when the foot and the top are moving at the same rate?