Use set.seed$(6751342)$ and split the economic data set into training and validation sets using $80\%$ and $20\%$ split, respectively. How many rows are in the original data set, the training set, and the validation set?

Use set.seed$(6751342)$ and create a regression decision tree for wage growth using economy, unemployment, and gdp as predictors. Include the cost$-$complexity $($cp$)$ table.

Plot the validation error against the cost$-$complexity parameter $($cp$).$ What is an appropriate cp value to use in pruning the tree?

Use set.seed$(6751342)$ and prune the tree using the appropriate cp value and include the plot of the resulting decision tree.