Standards for firewalls may be based on their thermal response to a prescribed radiant heat flux. consider a 0.25-m-thick concrete wall (rho= 2300 kg/m3, c= 880 j/kg·k, k= 1.4 w/m·k), which is at an initial temperature of ti= 25°c and irradiated at one surface by lamps that provide a uniform heat flux of qs′′= 0.85·104 w/m2. the absorptivity of the surface to the irradiation is αs= 1.0. if building code requirements dictate that the temperatures of the irradiated and back surfaces must not exceed 325°c and 25°c, respectively, after 30 min of heating, will the requirements b