13.16 Price, age, and horsepower In the previous exercise, r2 = 0.66 when age is the predictor and R2 = 0.69 when both age and HP are predictors. Why do you think that the predictions of price don’t improve much when HP is added to the model? (The correlation between HP and price is r = 0.56, and the correlation between HP and age is r = -0.51.)