4. A man is walking beside a 30m street lamp. After walking 25 m away from the street lamp, he sunk into a quicksand. At the time when 2 m of him are above the ground, he is sinking at 1 m/s. At What rate is the length of his shadow changing at that moment? 5. A spherical balloon is inated so that its volume is increasing at the rate of 2 mein. At What rate is the diameter increasing when the diameter is 6 m