$1\mathrm{.}3$ Product from a ball mill consists of spherical solid particles $)=(2\mathrm{.}5$ with the following size distribution:

$\backslash$table$[[$Diameter $(m),\%$ weight

Determine or calculate the following:

a$.$ Median diameter, $d_{50},$ and $d_{90}$

b$.$ Volume mean diameter, $d{v}_n$

c$.$ Surface area $-$ volume mean diameter, dsvn

d$.$ Specific surface areas, $av(\frac{m^2}{m^3})$ and as $(\frac{m^2}{k}g).$