A $500kg$ batch of wet solid is to be dried from an initial moisture content $($wet basis$)$ of $33\%$ to

a final moisture content $($wet basis$)$ of $7\%.$ The critical and equilibrium moisture contents $($dry

basis$)$ are $15\%$ and $3\%,$ respectively, the drying gas enters at $67C$ and $10\%$ humidity, and the

mass transfer coefficient of wet solid to air is $0\mathrm{.}05kg*m^{-2}*s^{-1}.$ Find the time required to complete

this drying process if the drying surface area is $1\mathrm{.}8m^2.$