Question

if a vehicle with a mass of 5,800lbs left skid marks that were 7ft. long, how fast were they going?
the concrete to tire coefficient of friction was .60

also, if a vehicle was 2,060lbs with skidmarks that were 20ft. long? same coefficient.

they're supposed to be going 45mph, and v2 was supposed to stop at a stop sign. did they run it?