(1 point) Suppose that z is a linear function of x and y with slope 3 in the x direction and slope 1 in the y direction. (a) A change of -0.4 in x and -0.2 in y produces what change in z? change in z = (b) If z = 8 when x = 2 and y = 5, what is the value of z when x = 2.1 and y = 5.1? Z=