You are shown a photo of a car driven on a vertical inside wall of a huge cylinder with a radius of 50 m. The coefficient of static friction between the car tires and the cylinder is μs=0.8. The minimum speed, at which the car can be driven like that, is:
(a) 20 km/h; (b) 70 km/h; (c) 90 km/h;
(d) 120 km/h.