Please note the two parts in this question are not related. [a] Find an equation of the tangent plane to the surface of z = 3ye'2xy'23'at (l, 2, 6). [bi Given that the function 2: = f(x,y) is a differentiable function with f(l,3) = 4, c(1,3) = 1, ll, 3) = 2, find the linear approximation and the differential of the function at [1.3]. Use the differential to estimate the total change oz when x is increased by 0.03, and y is decreased by 0.02. Enter your answer in the blank below. Round your answer to two decimal places