In an old-fashioned amusement park ride, passengers stand within a 3.0 m tall, 5.0 m diameter hollow steel cylinder with their backs alongside the wall. The cylinder starts to rotate around a vertical axis. Then the floor on which the passengers are standing all of a sudden drops away! If all goes well, the passengers will "stick" to the wall and not slide. Clothing consists of a static coefficient of friction against steel in the range .6 to 1.0 and a kinetic coefficient in the range of .4 to .7. Determine the minimum rotational frequency in rpm, for which the ride is secure?