Barton, Inc. has budgeted sales in units for the next five months as follows: June, 4,600 units; July, 7,200 units; August, 5,400 units; September, 6,800 units; October, 3,800 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 400 units. The company needs to prepare a Production Budget for the second quarter of the year. The opening inventory in units for September is: