$6-$ A drawing hall $40m25m$ is to be illuminated with lamps to an average illumination of $90l\frac{m}{m^2}$ with a mounting height of $5$ m $.$ Estimate suitable number and size of lamps. Sketch the spacing layout. Assume coefficient of utilization of $0\mathrm{.}5,$ depreciation factor of $0\mathrm{.}8.$ Consider that $1\frac{S}{H}1\mathrm{.}5.$

$\backslash$table$[[$Size of lamps,$200$ W$,300$ W$,500$ W$],[$Luminous efficiency $($in $l\frac{m}{W},16,18,25]]$