Q4. Consider the function f(x, y) = exp cos(C) ry + 1 my *-1, where exp(x} = er. a) Find the partial derivatives fr and fy of the function f. [2 marks] b) Find a normal vector to the graph S of f at P = (0, 1, f(0, 1)) and an equation for the tangent plane II to S at the point P. [2 marks]