An actuary wanted to develop a model to predict how long individuals will live. After consulting a number of physicians, she collected the age at death (v), the average number of hours of exercise per week (x), the cholesterol level (x), and the number of points that the individual's blood pressure exceeded the recommended value (x3). A random sample of 40 individuals was selected. The computer output of the multiple regression model is shown below. Coef Predictor Constant X1 x2 x3 S = 9.47 55.8 1.79 -0.021 -0.016 Error Total R-Sq=22.5% ANALYSIS OF VARIANCE Source of Variation Regression df 3 36 39 StDev 11.8 0.44 0.011 0.014 SS 936 3230 4166 4.729 4.068 -1.909 -1.143 MS 312 89.722 F 3.477 a. State the regression equation. b. Interpret the coefficient for the independent variable average number of hours of exercise per week. c. What percentage of the variability in age at death is explained by the model? d. What is the predicted age at death for an individual who exercised on average 10 hours weekly, had a cholesterol level of 190 mg/dl and was 10 points over the recommended blood pressure value