Find the equation of the tangent plane at the point x = x0 = 4, y = yo = 1 of the surface z = f (x, y ) = xyexty Select one: O a. z = 4e' + 8es(x - 4) + 5es (y - 1) O b. z = 4e' + 8es(x - 4) + 9e5 (y - 1) O c. None of these O d. z = 45 + 9es(x - 4) + 8es (y - 1) e. z = 405 + 5es(x - 4)+ 85(y - 1)