A $3-$m$-$high and $5-$m$-$wide wall consists of long $16-$cm $22-$cm cross section horizon$-$ tal bricks $($k $=0\mathrm{.}72$ W$/$m$$K$)$ separated by $3-$cm$-$thick plaster layers $($k $=0\mathrm{.}22$ W$/$m$$K$).$ There are also $2-$cm$-$thick plaster layers on each side of the brick and a $3-$cm$-$thick rigid foam $($k $=0\mathrm{.}026$ W$/$m$$K$)$ on the inner side of the wall, as shown in Fig. $321.$ The indoor and the outdoor temperatures are $20$C and $10$C$,$ respectively, and the convection heat transfer coefficients on the inner and the outer sides are h$1=10$ W$/$m$2$K and h$2=25$ W$/$m$2$K$,$ respectively. Assuming one$-$dimensional heat transfer and disregarding radiation, determine the rate of heat transfer through the wall. WHY WE ASSUME THE DEPTH OF THE WALL AS $1$M $????????$