Banked curves, coefficient of friction problem

[a321]

Homework Statement

A road with a radius of 74.8 m is banked so that a car can navigate the curve at a speed of 15 m/s without any friction. When a car is going 21.1 m/s on this curve, what minimum coefficient of static friction is needed if the car is to navigate the curve without slipping?

Homework Equations

The Attempt at a Solution

I figured out the angle by doing (v^2)/gr but I don't know how to find the coefficient of static friction. PLEASE HELP!

 

[ehild]

Draw a free-body diagram. The resultant of all forces has to be equal to the centripetal force. ehild