Tim's Treadmills uses the Periodic Inventory System and has a December 31st year-end. The company began the year with inventory with a cost of $20,450. When Tim's staff counted inventory at December 31, inventory with a cost of $24,750 were on hand. The company also had the following account balances for the year (random order, all with normal balances): Office Supplies Expense Purchases Sales Discounts Advertising Expense Interest Income Freight in Freight Out Sales-person Salaries Sales Returns and Allowances Loss on Sale of PP&E Purchase Returns and Allowances Sales Revenue Purchase Discounts Management Salaries $5,170 219,450 2,640 12,430 2,200 18,040 13,420 67,650 11,220 610 10,780 357,500 1,980 21,780 Required: 1) Prepare a detailed calculation of Gross Margin (in income statement form; show all account names used) for the year-ended December 31, 2021. (15 marks) Note: A full income statement is NOT required (just up to Gross Margin) All accounts above will NOT be used in the Gross Margin calculation (chose only those that are included in Net Sales and Cost of Goods Sold)