I don't understand where the box is marked

$.$

For the conditions of Example $24\mathrm{.}1$ except that $95$ percent of the gas is recirculated, calculate the operating conditions and the thermal efficiency. Use as a basis a section between two trays with an inlet area of $2$ ft x $0\mathrm{.}25$ ft or $0\mathrm{.}5$ ft$^2$ and a surface area of $2$ x $4=8$ ft$^2.$

$.$

$[$Example $24\mathrm{.}1]$

A filter cake $24$ in$.(610$ mm$)$ square and $2$ in$.(51$ mm$)$ thick, supported on a screen, is dried from both sides with air at a wet$-$bulb temperature of $80\backslash$deg F $(26\mathrm{.}7\backslash$deg C$)$ and a dry$-$bulb temperature of $160\backslash$deg F $(71\mathrm{.}1\backslash$deg C$).$ The air fiows parallel with the faces of the cake at a velocity of $8$ ft$/$s $(2\mathrm{.}44$ m$/$s$).$ The dry density of the cake is $1201$b$/$ft $(1,922$ kg$/$m$),$ The equilibrium moisture content is negligible, Under the con$-$ ditions of drying the critical moisture is $9$ percent, dry basis. $($a$)$ What is the drying rate during the constant$-$rate period? $($b$)$ How long would it take to dry this material from an initial moisture content of $20$ percent $($dry basis$)$ to a final moisture content of $10$ percent? Equivalent diameter D$,$ is equal to $6$ in$.(153$ mm$).$ Assume that heat transfer by radiation or by conduction is negligible.

$\{(])[$