$6($B$)$ Flow through granular$-$based porous media $($such as a mixture of water and crude oil through a layer of porous rock in fracking or hydraulic fracturing$)$ can be described by Ergun equation, which correlate the pressure drop per thickness of porous media $(\frac{p}{L})$ to the superficial velocity $($ U $),$ sand diameter $($ d $),$ porosity $()$ and viscosity $()$ as

$\frac{p}{L}=150\frac{(1-{)}^2}{{}^3}\frac{U}{d^2}+1\mathrm{.}75\frac{(1-)}{{}^3}\frac{U^2}{d}$

A set of data of are obtained for an unknown porous media of thickness $L$ and an unknown viscosity of fluid. Based on the least$-$square method, derive equations that can be used to determine the best estimate of granular diameter, porosity, and viscosity $($no need to solve these equations$)\mathrm{.}9$