Police use the formula to estimate the speed s of a car in…

Police use the formula to estimate the speed s of a car in miles per​ hour, where d is the distance in feet that the car skidded and f is the coefficient of friction. If the coefficient of friction on a certain dry road is 0.81 and a car was traveling on it at a rate of 30 mph, how far will the car​ skid? (Round to the nearest​ foot.)