PROBLEM $4$: $(5$ points$)$

Aucndarce wiowner:

$30$ Students occupy a classroom with a volume of $1000$ m $3$ with an absorption coefficient of ar$0\mathrm{.}46$ each. The room has the following surface finishes, Area, and absorption coefficients at $250Hz$:

$\backslash$table$[[,$Area,Abs Coeff.$],[$Walls$,$ plaster on brick,$100m^2,0\mathrm{.}02],[$Floors$,$ plastictiles,$80m^2,0\mathrm{.}05],[$Ceiling$,$ plasterboard on battens,$80m^2,0\mathrm{.}10]]$

At present, it has a very high Reverberation Time $($RT$)$ of $5\mathrm{.}863$ seconds. Calculate the amount of extra absorption $($the $\frac{?}{{?}_{\frac{?}{?}}A})$ required to obtain its optimum reverberation time of $1\mathrm{.}5$ sec $.$

Where: $RT=\frac{0\mathrm{.}163(V)}{A}$ in seconds.