Can someone help me with this radial acceleration problem? A curve with a radius of 88m is perfectly banked for a car traveling at 75 km/hr (approx. 20.83 m/s). What must be the coefficient of static friction for the car to not skid while going at 95 km/hr (26.389 m/s)?
I started by finding the radial acceleration at 75 km/hr and I got 4.93 m/s^2, and then I found the radial acceleration at 95 km/hr and got 7.91 m/s^2. I set it up like: m7.91 -uk mg = m 4.93 where uk is the coefficient of static friction. I ended up with .3 for uk, but that was wrong, so I guess I need help with set up.

Question

Can someone help me with this radial acceleration problem? A curve with a radius of 88m is perfectly banked for a car traveling at 75 km/hr (approx. 20.83 m/s). What must be the coefficient of static friction for the car to not skid while going at 95 km/hr (26.389 m/s)? 
I started by finding the radial acceleration at 75 km/hr and I got 4.93 m/s^2, and then I found the radial acceleration at 95 km/hr and got 7.91 m/s^2. I set it up like: m7.91 -uk mg = m 4.93 where uk is the coefficient of static friction. I ended up with .3 for uk, but that was wrong, so I guess I need help with set up.