The data set given in DS 13.2.4 extends the data set used in Problem 12.2.6 to include an individual's heart rate at rest, percentage body fat and weight, together with the variables age and V02-max considered before. Fit a multiple linear regression model to assess whether the new input variables heart rate at rest, percentage body fat. and weight, together with age, can be used to provide an improved model for V02-max. What model would you recommend? (This problem is continued in Problem 13.4.3.)