Physics Help Please, Friction?

You are called as an expert witness in the trial of a traffic violation. The facts are these: A driver slammed on his brakes and came to a stop with constant acceleration. Measurements of his tires and the skid marks on the pavement indicate that he locked his car's wheels, the car traveled 192 ft before stopping, and the coefficient of kinetic friction between the road and his tires was 0.750. The charge is that he was speeding in a 45 mi/h zone. He pleads innocent.

A) Is he guilty or innocent?

B) What was his velocity before he hit the brakes?