7. You are studying the effect of two traits on the evolution of sparrows. Let X represent the value of one trait, such as bill width, and let Y represent the level value of the other trait. such as wingspan. You have found that the following function models the fitness of individuals born with any given level of X and Y: f(X, Y) = 9X2 + 6Y2 4X3 2Y3 3X2Y2 This function has critical points at (0. 0). (0, 2), (1,1), and (1.5.0). a) Classify each critical point as a local maximum, local minimum, or saddle point. b) At what values of X and Y might you expect distinct species of sparrows to form? 8. Plants need nitrogen (N) and phosphorus (P) to grow, but both of these nutrients can become toxic at high concentrations. Suppose that the growth rate of a plant is given by g(N,P) =5(N3)2 (P2)2 Find the optimal nitrogen and phosphorus levels for this plant. Make sure to check that your critical point really is the maximum