I need an explanation for each step, as well as where they would go on the tabular summary.

Assume that on September 1, Office Depot had an inventory that included a variety of calculators. The company uses a perpetual inventory system. During September, these transactions occurred. Sept. 6 Purchased calculators from Oriole Co. at a total cost of $1,815, on account, terms n/30. 9 Paid freight of $55 on calculators purchased from Oriole Co. 10 Returned calculators to Oriole Co. for $68 credit because they did not meet specifications. 12 Sold calculators costing $566 for $762 to Pharoah Book Store, on account, terms n/30. 14 Granted credit of $51 to Pharoah Book Store for the return of one calculator that was not ordered. The calculator cost$42 20 Sold calculators costing $621 for $833 to Sheridan Card Shop, on account, terms n/30. Prepare a tabular summary to record the transactions for the month of September for Office Depot using a perpetual inventory system. Include margin explanations for the changes in revenues and expenses. (Enter negative amounts using either a negative sign preceding the number e.g. -45 or parentheses e.g. (45).)