Ex 14.5.18 A bug is crawling on the surface of a hot plate, the temperature of which at the point a units to the right of the lower left corner and y units up from the lower left corner is given by T(x,y) = 100 - x - 3y. a. If the bug is at the point (2,1), in what direction should it move to cool off the fastest? How fast will the temperature drop in this direction? b. If the bug is at the point (1,3), in what direction should it move in order to maintain its temperature?