Roberts Enterprises has budgeted sales in units for the next five months as follows: June July August September October 4,500 units 7,100 units 5,300 units 6,700 units 3,700 units Past experience has shown that the ending inventory for each month must be equal to 10% of the next month's sales in units. The inventory on May 31 contained 450 units. The company needs to prepare a production budget for the second quarter of the year. The beginning inventory in units for September is