An automobile crash investigator measured the skid marks of a vehicle involved in a crash. The length of the skid marks was 86 feet. Using the formula s = √(24d), where s is the speed of the vehicle in miles per hour before the brakes were applied, and d is the length of the skid marks in feet, what was the speed of the vehicle before it started braking? Round your answer to the nearest tenth.
a) 28.9 mph
b) 32.9 mph
c) 36.9 mph
d) 40.9 mph