Problem 4 Continuity and Differentiability . Consider the function f(r, y) = if (x, y) # (0,0). if (x, y) = (0,0). (i) Give the most obvious reason why f (r, y) is not differentiable at (0, 0). (ii) Use the limit definition of a partial derivative to compute /, (0, 0) and f (0,0). In light of part (i) what is your conclusion about the differentiabilty of the function /(r, y) at (0, 0)