Calculate the mass of each of the constituents needed per unit mass to prepare fiber$-$reinforced composites with the following compositions

$($a$)$ polypropylene reinforced $30$vol $\%$ of glass fibers

$($b$)$ epoxy resin reinforced by a combination of $20$ vol. $\%$ carbon fiber and $30$ vol. $\%$ aramid fibers

$($data: density of polypropylene $0\mathrm{.}90$ ; density of glass fibers: $2\mathrm{.}54$ ; density of epoxy resin: $1\mathrm{.}30$; density of carbon fibers $1\mathrm{.}79$ ; density of aramid fibers $1\mathrm{.}45$; all units are in $\frac{Mg}{m^3})$