Friction Coefficients and Minimum Normal Force

[Sligh]

Homework Statement

The 68 kg climber in Fig. 4-52 is supported in the "chimney" by the friction forces exerted on his shoes and back. The static coefficients of friction between his shoes and the wall, and between his back and the wall, are 0.78 and 0.55, respectively. What is the minimum normal force he must exert? Assume the walls are vertical and that friction forces are both at a maximum.

2. The attempt at a solution

I have drawn some free body diagrams, but I cannot quite grasp this question. Any help towards a solution would be greatly appreciated.

 

[Doc Al]

Well, what forces act on the climber? What's the net force?

 

[Sligh]

Thanks anyhow. I figured it out now. ;)