S$.$ In a period, $9000$ units were made and there was a favourable labour efficiency variance of $$58000.$ Employees were paid $$10$ per hour, total wages were $$340000$ and there was a nil labour rate variance.

How many standard labour hours were there per unit $($to the nearest decimal place$)?$

$\backslash$table$[[$A$,[,3,3\mathrm{.}1],[$B$,[,],3\mathrm{.}8],[$C$,[,],4\mathrm{.}4],[$D$,[,$They cannot be calculated without more information.,$]]$