1. (a) If V is the volume of a cube with edge length x and the cube expands as time passes, nd dV/dt in terms of dx/dt. (b) If the length of the edge of a cube is increasing at a rate of 4 cm/s, how fast is the volume of the cube increasing when the edge length is 15 cm? 2. (a) If A is the area of a circle with radius r and the circle expands as time passes, nd dA/dt in terms of dr/dt. (b) Suppose oil spills from a ruptured tanker and spreads in a circular pattern. If the radius of the oil spill increases at a constant rate of 2 m/s, how fast is the area of the spill increasing when the radius is 30 m