Calculate the distance from the axis beyond which the particles have slid off a rotating disk

A collection of small particles is distributed on the top surface of a disc that is rotating at 91 revolutions per second, about an axis, which is vertical. Some of the particles slide off, and some remain in place. Take the coefficients of kinetic and static friction between particles and the disc as 1.1 and 1.5 respectively. Calculate the distance from the axis beyond which the particles have slid off.

I am kind of confused about what the free body diagram would look like. Centripetal force is to the centre. What direction is the normal? Also, what does it mean by “distance from the axis beyond which the particles have slid off”? Where is this distance measured from? Is it the distance from which the particles start to fly off? I am struggling with most of this question.