The income statements of Sheridan Corporation show the following amounts: 2020 2019 2018 Net sales $750 $720 $670 Cost of goods sold 510 482 426 Gross profit 240 238 244 Selling, general, and administrative expenses 180 142 105 Profit before tax 60 96 139 Using vertical (common-size) analysis, analyze Sheridan Corporations declining profit before tax. (Round answers to 0 decimal places, e.g. 52%.) 2020 2019 2018 Net sales % % % Cost of goods sold % % % Gross profit % % % Selling, general, and administrative expenses % % % Profit before tax % % %