$2-$ A thick$-$walled cylinder with $0\mathrm{.}10$ m internal diameter and $0\mathrm{.}15$ m external diameter is

fabricated of a material whose yield strength is $400$ MPa and Poisson's ratio $v=0\mathrm{.}3.$ The

cylinder is subjected to an internal pressure seven times greater than the external pressure.

Calculate the allowable intemal pressure according to:

a$)$ the maximum shear stress criterion

b$)$ the Von$-$Mises criterion