friction question

Question

A car is traveling at 25 m/s along a horizontal road. The coefficients of friction between the road and the tires are us=0.95 uk=0.34.Calculate the distance the car travel before stopping if the car is braked with an antilock braking system so that threshold braking is sustained.Take g=9.81 

Answer 1

F = μN = μmg = m*a so μ*g = a so a = 0.34*9.8 which is the abs(a) because acceleration is really negative since it's in opposite direction

V_f2 = 0 = V² + 2ad... 25/(2a) = d... the negative cancelled out because acceleration was really negative

so d = 25/2(.34*9.8) = 3.7515 m