(10 pts) A large ice cube is put into a hot oven and is melting. Assume it always stays cubical in shape. At a certain moment in time the volume of the cube is decreasing at a rate of and the edge length is . b. (4 pts) Suppose the cube melts at a rate proportional to its surface area , that is, , where is the constant of proportionality. Show that the edge length decreases at a constant rate as the cube melts. Then determine the constant and show its units. . 2 / min 3 in x =10 in x x x 2 S x = 6 dV k S dt = −  k x k 3 V x =