Find the minimum value of the average cost for the given cost function on the given intervals. K C(x) =x +28x+128 (a) 13x310 (b) 10sx5 20 (a) The minimum value of the average cost over the interval 1 x$ 10 is (Round to the nearest tenth as needed. Do not include the $ symbol in your answer.) (b) The minimum value of the average cost over the interval 10 Sx $ 20 is (Round to the nearest tenth as needed, Do not include the $ symbol in your answer.)