Static friction between two surfaces

If the static friction between two surface P and Q is measured to be 50 N, then the sliding friction between these two surface is most likely to be :

If the static friction between two surface X and Y is found to be 20 N, then the rolling between these two surfaces should most likely be :

The limiting friction between two surfaces depends

What is the angle of friction, if the coefficient of friction between two surfaces is 0.25 ?

The limiting friction between two surface does not depend