The inventory records for Radford Co. reflected the following: Beginning inventory @ May 1 1500 units @ $4.60 First purchase @ May 7 1600 units @ $4.80 Second purchase @ May 17 1800 units @ $4.90 Third purchase @ May 23 1400 units @ $5.00 Sales @ May 31 4800 units @ $6.50 What is the amount of gross margin assuming the FIFO cost flow method? Select one: O a. $7700 O b. $9120 O c. $23,184 O d. $8290