The fictional Taj Mahal Indian grocery store had sales of US $50,000 in August and US $62,000 in September. There are 10 full-time workers in the store, each of whom worked 40 hours a week. In August, the store also employed six part-time workers, each of whom worked 15 hours a week. In September, eight part-time workers were employed, each for 10 hours a week. Assuming there are four weeks in each month, and sales dollars are the output measure, what was the change in productivity from August to September?