On September 1, the beginning of its fiscal year, Campus Office Supply Ltd. had an inventory of 106 calculators at a cost of $20 each. The company uses a perpetual inventory system. During September, the following transactions occurred: Sept. 2 Purchased 795 calculators for $20 each from Digital Corp. on account, terms n/30. 10 Returned 21 calculators to Digital for $420 credit because they did not meet specifications. 11 Sold 340 calculators for $30 each to Campus Book Store, terms n/30. Management estimates returns of 4% based on prior experience. 14 Granted credit of $630 to Campus Book Store for the return of 21 calculators that were not ordered. The calculators were restored to inventory. 29 Paid Digital the amount owing. 30 30 Received payment in full from the Campus Book Store.