11. Suppose that z is a linear function of x and y with slope 2 in the x-direction and slope 3 in the y-direction. (a) A change of 0.5 in x and -0.2 in y produces what change in z? (b) If z = 2 when x = 5 and y = 7, what is the value of z when x = 4.9 and y = 7.2? 12. (a) Find a formula for the linear function whose graph is a plane passing through point (4,3, -2) with slope 5 in the x-direction and slope -3 in the y- direction. (b) Sketch the contour diagram for this function.For Problems 21-22, find a possible equation for a linear function with the given contour diagram. 21. X L -2 -3 -3 -2 -1 1 2 3 22. - NW X - 1 -2 -3 -3 -2 -1 1 2 3