Common-size and trend percentages for a company's net sales, cost of goods sold, and expenses follow Common-Size Percentages Trend Percentages 2017 2016 2015 2017 2016 2015 Net sales Cost of goods sold Expenses 100.0% 48.3 31.6 100.0% 45.8 28.4 100.0% 107.4% 105.7% 100.0% 42.9 115.2111.2 100.0 30.0 109.7 104.1 100.0 Required: a. Calculate the profit percentage for 2015, 2016 and 2017. (Round the final answers to 2 decimal places.) Profit Percentage 2015 2016 2017 b. Determine whether the company's profit increased, decreased, or remained unchanged during this three-year period Profit