Shear Strength - III: Problem #1

The following problem has been taken directly from my notes (in my graduate school):

For the soil element shown, determine the maximum and minimum principal stresses, the maximum shear stress and its corresponding normal stress, and the normal and shear stresses on plane AB. Use the following methods,
a.) by using equations
b.) by using Mohr's circles
c.) by using the Origin of Planes

I'll post the solution tomorrow. If anyone is interested in reading further, I would recommend, "An Introduction to Geotechnical Engineering" by Holtz and Kovacs.