6. The Frailty Index FI34 is a quantitative measure of biological aging based on 34 health variables. The figure below shows fitted regression lines for a multiple regression model of FI34 on age and an indicator variable for whether a person walks at least 30 minutes per day (Walker =1 if the person walks 2 30 mins/day and 0 if not). Non-Walker = = = Walker Frailty Index Fly4 Age Which equation is consistent with the fitted regression lines: a. E[FI;4] = 0.07 + 0.004 x Age + 0.02 x Walker b. E[Fla4] = 0.07 + 0.004 x Age - 0.02 x Walker C. E[FI34] = 0.07 - 0.004 x Age - 0.02 x Walker d. E[Fly,] = 0.07 - 0.004 x Age + 0.02 x Walker e. E[FI),] = 0.004 x Age - 0.02 x Walker