For each of the two-variable-factor production functions listed below, deduce the sign and magnitude that each parameter must have for the function to be well-behaved. Then, sketch TPP, APP, and MPP for factor x1 for each function a. y=b 1x 1+b 2x 2b. y=a 1x 1+a 2x 2+b 1x 12+b 2x 22 +b 3x 1 x 2