Lifting a prism; coefficient of friction

[kate12]

Homework Statement

A prism has a mass of m = 80 g, and you wish to lift it, touching
the upper two faces only. If the coecient of friction between the prism’s surface and
your skin is  = 0:4, what is the minimum force that must be applied to each face?

Homework Equations

F=μR

The Attempt at a Solution

I drew the forces perpendicular to the two surfaces. I don't really know how to resolve them, and how F=μR comes into it.

 

[Infinitum]

The question seems incomplete without mentioning what kind of prism it is...You cannot resolve the forces to anything useful. if you don't know the prism angle.

 

[azizlwl]

We need a net force equal the weight of the prism, passing thru the centre of mass.
This net force is equal to the resultant of 2 forces, each from each finger.
The force from each finger is equal or less than maximum static friction between finder and prism.
The static friction is equal μN where N equal to force applied if it is applied perpendicularly to the plane of the prism.