A building constructed from composite walls has a design specification stating a maximum permissible heat transfer of 200 W/m2. The internal wall section thickness has been set as 80mm whilst the external section thickness has to be proposed by you. Using a specified interior wall temperature of 90oC and exterior wall temperature of 20oC for the second room propose a suitable wall thickness for section 2 showing all of your heat transfer calculations . You can assume that both wall sections, 1 & 2, have similar area A = 3.5 m2 whilst the thermal conductivity of the materials are k1 = 0.5 W/mk and k2 = 0.07 W/mk respectively.4