The stopping distance of an automobile can be determined by combining the reaction time of the driver and the breaking distance required to stop the car. The reaction time is measured in feet traveled and is given by the function r(x)=3/4x+2 where x is the speed of the vehicle in mph. The distance traveled while the driver is breaking is given by the function b(x)=1/15x^2−12x where x is the speed of the vehicle in mph. Write a function d(x) for the total stopping distance. Calculate d(60) and interpret its meaning in context.