The accompanying data file contains information on the sale price (in $) for 36 single-family homes in Arlington, Massachusetts. In order to analyze house price, the predictor variables include the house’s square footage (Sqft), the number of bedrooms (Beds), the number of bathrooms (Baths), and whether or not it is a colonial (Col = 1 if colonial, 0 otherwise). 

a. Use the holdout method to compare the predictability of the linear and the exponential models using the first 24 observations for training and the remaining 12 observations for validation. 

b. Use the k-fold cross-validation method to compare the predictability of the models using k = 3.