The drying of a food product occurs during the falling-rate period between the critical moisture content of 0.58 kg water/kg solids and a final moisture content of 0.22 kg water/kg solids. The product, with 1 cm thickness and a 6 cm by 13 cm surface, is exposed to the heated air. The equilibrium moisture content is 0.2 kg water/kg solids. If the constant drying rate is 0.3 kg H2O/(m² s), estimate the falling-rate drying time. The product density is 675kg / (m ^ 3).