1. Consider the function ry(x? 92 f(e,y) = W if (z,y) # (0,0) (a) [1p] Find the value k R for which the function f is continuous. (b) [1p] For the value k found in part (a), show that f is differentiable at (0, 0). BQ (optional) (c) [1p] For the value k found in part (a), find the second order partial derivatives f,, and f,, of f. BQ (optional)(d) [1p] Does your result in part (c) contradict Clariaut's theorem? Fully justify your