A boiler is made of a copper plate 2.4 mm thick with an inside coating of a 0.2 mm thick layer of tin. The surface area exposed to gases at 700°C is 400cm² . The maximum amount of steam that could be generated per hour at atmospheric pressure is
${\text{(K}}_{\mathrm{cu}}=0.9\mathrm{cal}/\mathrm{cm}-\mathrm{s}{-}^0\mathrm{\&}{\mathrm{k}}_{\mathrm{tin} }=0.15\mathrm{cal}/\mathrm{cm}-\mathrm{s}{-}^0\mathrm{C} \mathrm{and} {\mathrm{L}}_{\mathrm{steam} }=540\mathrm{cal}/\mathrm{g})$