The wall of a bakery oven is built of insulating brick $10cm$ thick and thermal conductivity $0\mathrm{.}22J{m}^{-1}{s}^{-1}{C}^{-1}.$ Steel reinforcing members penetrate the brick, and their total area of cross$-$section represents $1\%$ of the inside wall area of the oven. If the thermal conductivity of the steel is $45J{m}^{-1}{s}^{-1}{C}^{-1}$ calculate $($a$)$ the relative proportions of the total heat transferred through the wall by the brick and by the steel and $($b$)$ the heat loss for each $m^2$ of oven wall if the inner side of the wall is at $230C$ and the outer side is at $25C.$