The accompanying data file contains 53 weeks of Apple’s stock price data. For cross-validation, let the training and the validation sets comprise the first 40 weeks and the last 13 weeks, respectively. 

a. Use the training set to implement the Holt exponential smoothing method with user-supplied (α = 0.20 and β = 0.10), as well as the computer-generated, smoothing parameters and compute the resulting MSE, MAD, and MAPE for the validation set. 

b. Determine the preferred model and reimplement it with the entire data set to forecast Apple’s stock price for the 54th week.