please show detailed work, im stuck.

4. The following selected transactions occurred at Mountain Hats, Inc. during the month of September (its first month of operations). Mountain Hats currently sells only one product - specialty ski hats with built-in speakers and Bluetooth capability. The company uses the perpetual inventory method. The hat sell for a retail price of $50.00 each. (1) September 1: Purchased 100 hats for its inventory from its supplier for $28.00 each with cash. (2) September 4: Sold 16 hats to Sun 'N' Ski Sports on credit, with terms 2/10, n/30. (3) September 6: Sold 30 hats to REI on credit with terms 2/10, 1/30. (4) September 7: Sold two hats directly to a customer, who charged the purchase to her Visa credit card. Visa charges Mountain Hats, Inc. a 3 percent credit card fee. (5) September 9: Collected payment from Sun 'N' Ski Sports for the September 4th sale. (6) September 13: REI returned 10 hats back to Mountain Hats due to ordering the wrong color. (7) September 14: Collected payment from REI for the remainder of its purchases on September 6th A. What is the ending balance in Mountain Hat's "Inventory" account at the end of September? B. Please list the title and ending balance of each contra-revenue account affected by the above transactions. Title Ending Balance c. What is Mountain Hats, Inc.'s Gross Profit for the month of September