Finding Minimum Coefficient of Friction to Keep Object Spinning in Vertical Circle for Falling

3. On the rotor ride the passengers stand against the wall of a small, circular room that spins in a circle. The radius of the room is 5.0 m. When the room is spinning fast enough, the floor drops down and the passengers stick to the wall. The period of the motion is 0.77s. What must be the minimum COEFFICIENT of FRICTION between the wall and the passenger if the passenger does not slide down?