Experimentally, it has been observed for single crystals of a number of metals that the critical resolved shear stress, $\tau_{crss}$, is a function of the dislocation density, $\rho_D$, as
$\tau_{crss} = \tau_0 + A\sqrt{\rho_D}$
where $\tau_0$ and A are constants. For some metal, the critical resolved shear stress is 2.11 MPa at a dislocation density of $2.90 \times 10^5$ mm$^{-2}$. If it is known that the value of A for this metal is $4.46 \times 10^{-3}$ MPa-mm, compute the $\tau_{crss}$ (in MPa) at a dislocation density of $1.13 \times 10^7$ mm$^{-2}$.
