On March 12, Fret Company sold merchandise in the amount of $7,800 to Babson Company, with credit terms of 2/10, n/30. The cost of the items sold is $4,500. Fret uses the perpetual inventory system and the gross method of accounting for sales. On March 15, Babson returns some of the merchandise. The selling price of the merchandise is $600 and the cost of the merchandise returned is $350. Babson pays the invoice on March 20 and takes the appropriate discount. The amount that Fret receives from Babson on March 20 is