$2.($SHOW YOUR COMPLETE WORK$)$ A retail store had sales of $$870,000$ in June and $$850,000$ in July. The store has $12$ full$-$time employees and each employee works $8$ hours per day. In the month of June, the store also had $5$ part$-$time employees and each part$-$time employee worked $4$ hours per day. In the month of July, the store also had $4$ part$-$time employees and each part$-$time employee worked $5$ hours per day. Assume that there are $20$ work days in June and $23$ work days in July. a$.$ Find the labor productivity $($expressed in sales dollars earned per labor$-$hour$)$ for the month of June. $[6$ points$]$b$.$ Find the labor productivity $($expressed in sales dollars earned per labor$-$hour$)$ for the month of July. $[6$ points$]$c$.$ Find the percentage change in labor productivity from June to July.