Inelastic Collision

1. The problem statement, all variables and given/known data
A Cadillac of mass 2250 kg going east collides with a Geo of mass 1180 kg headed north on a level highway. The cars remain tangled and slide to rest after traveling 25 m in a straight line at an angle of 20° north of east. The coefficient of kinetic friction for the tires on the road is 0.2. How fast was the Cadillac traveling before the unfortunate collision?

2. Relevant equations
Frictional Force = coefficient of friction x normal force, inelastic collision, conservation of momentum, motion formulas.

3. The attempt at a solution
Did not know how to approach problem.

Thanks for the help

 

With the coefficient of kinetic friction, am I suppose to use it with normal force to find frictional force?

And also, I don't really understand how frictional force applies to deceleration.