Ecology Co. sells a biodegradable product called Dissol and has predicted the following sales for the first four months of the current year: Jan. Feb. March. April. Sales in units 3,500 4,600 5,700 4,300 Ending inventory for each month should be 20% of the next month's sales, and the December 31 inventory is consistent with that policy. How many units should be purchased in February?