22. This question refers to Problem 21. a. Fit the random model given by Equation 3.4 to the data in Table P-21 by estimating c with the sample mean ybar so Y(t)^ = ybar. Compute the residuals using e(t) = Y(t) y(t)^ = y ybar. b. Using Minitab or a similar program, compute the autocorrelations of the residuals from part c for the first 10 time lags. Is the random model adequate for the sales data? Explain. Table P-21 Weekly Sales Of a Food Item 2649.9 2898.7 2897.8 3054.3 3888.1 3963.6 3258.9 3199.6 3504.3 2445.9 1833.9 2185.4 3367.4 1374.1 497.5 1699.0 1425.4 1946.2 1809.9 2339.9 1717.9 2420.3 1396.5 1612.1 1367.9 2176.8 2725.0 3723.7 2016.0 862.2 1234.6 1166.5 1759.5 1039.4 2404.8 2047.8 4072.6 4600.5 2370.1 3542.3 2273.0 3596.6 2615.8 2253.3 1779.4 3917.9 3329.3 1864.4 3318.9 3342.6 2131.9 3003.2