Given radius of circular level road, r=300 m
Coefficient of static friction, μ=0.3
For maximum safe speed, friction will act at its limiting value to provide necessary centripetal force and prevent skidding of car.
f=mv2r
⇒μmg=mv2r
⇒v=√μrg
⇒v=√0.3×300×10
∴v=30 m/s=30×185=108 km/h
[∵1 m/s=185 km/h]
Maximum safe speed of the car is 108 km/h.