Q4 (9 points) Consider the function f(r, y) = 9e2x-2 sin y + 22. (a) Find the rate of change of f(x, y) at the point P : (1, , ) in the direction from P to point Q : (2, 7). (b) If u is a unit direction vector in the same direction as P to Q, what is the value of D_i f(P)? (c) If a mountain range is given by z = f(x, y), what direction from point P gives the steepest descent? What is the rate of change that you will experience if you walk in this direction