The inventory records for Radford Co. reflected the following:

Beginning inventory @ May 1 1,400 units @ $4.40

First purchase @ May 7 1,500 units @ $4.60

Second purchase @ May 17 1,700 units @ $4.70

Third purchase @ May 23 1,300 units @ $4.80

Sales @ May 31 4,500 units @ $6.30

What is the amount of gross margin assuming the weighted-average inventory cost flow method?