Use the data set Credit from the R library ISLR. You will build linear models to predict the response Rating.

(1) Build a simple linear regression model with Income as the predictor, provide a summary of the fitted model, and show diagnostic plots for the model. 

(2) Build a multiple linear regression model with Income, Gender and Cards as predictors, provide a summary of the fitted model, the variance inflation factor for each predictor, and show diagnostic plots for the model. Caution:  make sure each predictor has the correct R object type; otherwise your model may be insensible. 

(3) Build a multiple linear regression model with all potential predictors in the data set, provide a summary of the fitted model, the variance inflation factor for each predictor, and show diagnostic plots for the model. 

Caution:  make sure each predictor has the correct R object type; otherwise your model may be insensible.