A retail store had sales of $$45,000$ in April and $$56,000$ in MayThe store employs eight full$-$time workers who work a $40-$hour week April, the store also had seven part$-$time workers at hours per week, and in May the store had nine part$-$timers at $15$ hours per week $($assume four weeks in each month $).$ Using sales dollars as the measure of output, what is the percentage change in productivity $($output in dollars per labor hour$)$ from April to May $?$