You are driving at a fixed speed of 30 km/hr. When you drive over a semi-circular speed bump, the wheels of the car begin to lose contact (just barely) with the road at the top of the bump. (Hint: Think about which force goes to zero when this happens. Also, you don't need to worry about the role of friction in this problem.) The radius of the bump is closest to:

a) 28.3 m b) 19.7 m c) 8.11 m d) 12.6 m e) 7.09 m