Problem $7\mathrm{.}13$

Problem Statement: A strain gauge rosette, as in Ex$.6\mathrm{.}9,$ is applied to the surface of a component made of $7075-$T$6$ aluminum. Assume that no yielding has occurred, and also that no loading is applied directly to the surface, so that ${}_{zz}={}_{yz}={}_{xz}=0.$ Strains are measured as follows: ${}_{}=1200{10}^{-6},{}_{yy}=-650{10}^{-6},$ and ${}_{45}=1900{10}^{-6}.$ What is the safety factor against yielding?