A 40-cm-thick brick wall $\left(k=0.72 \mathrm{~W} / \mathrm{m} \cdot{ }^{\circ} \mathrm{C}\right.$, and $\alpha=1.6 \times 10^{-7} \mathrm{~m}^2 / \mathrm{s}$ ) is heated to an average temperature of $18^{\circ} \mathrm{C}$ by the heating system and the solar radiation incident on it during the day. During the night, the outer surface of the wall is exposed to cold air at $-3^{\circ} \mathrm{C}$ with an average heat transfer coefficient of $20 \mathrm{~W} / \mathrm{m}^2 \cdot{ }^{\circ} \mathrm{C}$, determine the wall temperatures at distances 15,30 , and 40 cm from the outer surface for a period of 2 h .