Q$4(30/100).$ Wind at $6C$ and $30k\frac{m}{h}$ is blowing parallel to a $2$ m high, $4$ m long, and $0\mathrm{.}4$ m thick wall whose representative cross section is as given in the figure. The thermal conductivities of various materials used, in $\frac{W}{m}C,$ are $k_A=4,k_B=10,k_C=20$ and $k_D=3.$ The temperature of the right surface of the wall is uniform and measured as $9C(T_2).$ Assuming heat transfer through the wall to be one$-$dimensional, determine the left surface temperature of the wall $(T_1).$