Whispering Company's record of transactions concerning part $x$ for the month of April was as follows.

$\backslash$table$[[$Purchases$,$Sales$],[$April$,1,($balance on hand$),300,$@$,$$$6\mathrm{.}10,$April,$5,500],[,4,,600,$@$,6\mathrm{.}20,,12,400],[,11,,500,$@$,6\mathrm{.}50,,27,1,200],[,18,,400,$@$,6\mathrm{.}50,,28,150],[,26,,800,$@$,6\mathrm{.}80,,,],[,30,,400,$@$,7\mathrm{.}10,,,]]$

$($a$1)$

Calculate the weighted$-$average cost per unit. $($Round answer to $4$ decimal places, e$.$g$.2\mathrm{.}7682.)$

Weighted$-$average cost per unit $