$2.)$ An iron $(G=82$GPa,$v=0\mathrm{.}29,b=0\mathrm{.}248nm)$ single crystal $(1cm1cm1cm)$ is sheared such that the plastic shear strain is $1\%.$ How many dislocations are required for this deformation? If the original dislocation density was $\frac{{10}^5}{m^2},$ what is the change in the dislocation self energy after this deformation $($assume all edge dislocations$)?$