$24\mathrm{.}3.$ A slab with a wet weight of $5kg$ originally contains $50$ percent moisture $($wet basis$).$ The slab is $600$ by $900$ by $75mm$ thick. The equilibrium$-$moisture content is $5$ percent of the total weight when in contact with air of $20C$ and $20$ percent humidity. The drying rate is given in Table $24\mathrm{.}1$ for contact with air of the above quality at a definite velocity. Drying is from one face. How long will it take to dry the slab to $15$ percent moisture content $($wet basis$)?$

TABLE $24\mathrm{.}1$

Data for Prob. $24\mathrm{.}3$

$$ Wet$-$slab weight, $kg$

$$ Drying rate, $k\frac{g}{m^2}-h$