The average rate at which energy is conducted outward through the ground surface in North America is $54.0$ $\mathrm{mW} / \mathrm{m}^{2}$, and the average thermal conductivity of the near-surface rocks is $2.50 \mathrm{~W} / \mathrm{m} \cdot \mathrm{K}$. Assuming a surface temperature of $10.0^{\circ} \mathrm{C}$, find the temperature at a depth of $35.0 \mathrm{~km}$ (near the base of the crust). Ignore the thermal energy transferred from the radioactive elements.