(4) (a) [8 pts] A 5 m ladder is leaning against a house when its base starts to slide away. By the time the base is 3 In from the house, the base is moving at the rate of 1.6 rn/sec. At what rate is the area of the triangle formed by the ladder, wall, and ground changing then? (b) [8 pts] Two carts, A and B , are connected by a rope 35 ft long that passes over a pulley P (see the gure below.) The point Q is on the oor 12 ft directly beneath P and between the carts. Cart A is being pulled away from Q at a speed of 4 ft / s. How fast is cart B moving toward Q at the instant when cart A is 9 ft from