(4) (2 point) In class, we showed Vf(x) is the direction in which a differentiable f increases the most. (a) What is the direction that f decreases the most? (Use similar analysis we did in class to justify your answer). (b) Suppose you are walking on a surface with elevation modeled by Find a direction x + y 20 2 = 2+ unit vector in R) from the point (2, 2) in which the rate of increase is half that of the maximum direction.