This problem involves the video game sales with ratings. We will fit regression models in order to predict global sales of video games.

a) Take the first 500 observations as the training set and use the rest asthe test set.

b) Fit a regression tree to predict Global_Sales. Use only the training set to fit the regression model. Determine the number of terminal nodes using cross-validation.

c) Predict Global_Sales in the test set using the regression tree model obtained in (b). Calculate the Root Mean Square (RMSE) of the regression tree.