3. Skim milk with initial moisture content of 19 kg water/kg solids is being spray dried to a final moisture content of 0.042 kg water/kg solids, using air at 120°C (dry bulb) and 7% RH at 57.1°C (wet bulb). The latent heat of vaporization at is 2354kJ/kg and thermal conductivity is 0.032 kW/m°C. The density of the skim milk product is 1000 kg/m³, and the largest droplet diameter is 120 μm. The critical moisture content is 0.818 kg water/kg solids, and the diameter of the particle at the critical moisture content is 25.5 μm. The equilibrium moisture content is 0.04 kg water/kg solids, and the mass diffusivity for water vapor within the particle is 5x10-11 m²/s. Analyse items below based on information above: a) Constant rate drying time (s/kg solid) based on droplet radius. b) If the mass of solid is 4.52 x10-11 kg solid/droplet, find constant time in seconds. c) Falling rate drying time based on particle radius (s) d) Total drying time (s)