How rate determining step can be find in a fluid solid catalyzed reaction? Explain in detail.

In an experiment to determine the pore volume and catalyst particle porosity, the following data is obtained on a sample of activated silica $($granular$,4$ to $12$ mesh size$)$

Mass of catalyst sample of activated silica $=101\mathrm{.}5gm$

Volume of helium displaced by the sample $=45\mathrm{.}1c{m}^3$

Volume of mercury displaced by the sample $=82\mathrm{.}7c{m}^3$

Calculate the the following :

$($a$)$ pore volume,

$($b$)$ void fraction,

$($c$)$ density of the particles and

$($d$)$ density of solid.

$(15]$