Matrix Plot of Pages X1, Competing Bo, Advertising, Age of Autho Based on the output to answer the following questions: 1. Use Matrix Plot of x1,x2,x3, and x4 to determine if there is evidence of collinearity in the four explanatory variables? 2. This was a designed experiment with non-random explanatory variables. Was it really necessary to investigate collinearity in this type of study? 3. Use a variable selection procedure with maximum R2 as the criterion to formulate the model. 4. Use a variable selection procedure with maximum R2 adj as the criterion to formulate the model 5. Use a variable selection procedure Cp as the criterion to formulate the model. 6. Compare the results of parts (3) (4) and (4). Which model is the best? and why