A cylindrical rod of steel $\left(E=207 \mathrm{GPa}, 30 \times 10^{\circ}\right.$ psi) having a yield strength of $310 \mathrm{MPa}(45,000$ psi) is to be subjected to a load of $11,100 \mathrm{~N}$ (2500 $\left.\mathrm{Ib}_{i}\right)$. If the length of the rod is $500 \mathrm{~mm}(20.0 \mathrm{in}$.), what must be the diameter to allow an elongation of $0.38 \mathrm{~mm}(0.015$ in.)?