Li Retailing reported the following items for the current year: Sales = $3,000,000; Cost of Goods Sold = $1,500,000; Depreciation Expense = $170,000; Administrative Expenses = $150,000; Interest Expense = $30,000; Marketing Expenses = $80,000; and Taxes = $300,000; Li's operating profit margin is equal to?

I know the answer is 36.67% but I would like to know what formula was used to determine that answer