Nucor Corporation produces steel and steel products at its eight mills and is a major recycler of scrap metal. The following data relate to Nucor for four years. In 2017, Nucor's net income was higher by $175.2 million because of a one-time effect of the Tax Cuts and Jobs Act.

Nucor Corporation ($ in millions) 2015 Total assets 2016 2017 2018 $14, 327.0 Common stockholders' equity $15 , 223.5 $15 , 841.3 $17, 920.6 Total debt 7, 849.9 8, 254.7 9, 084.8 10, 202.0 4, 388.5 Sales 4, 357.1 3, 795.1 4 , 291.1 Net income 16, 208.1 20, 252.4 25, 067.3 900.4 Interest expense 1, 380.6 2, 481 .1 Assumed marginal income tax rate 169.2 173.6 135.5 0.37 0.37 0. 23Required 1 Required 2 Required 3 Required 4 Decompose ROA into operating profit margin and asset turnover components. (Do not round intermediate calculations. Round your answers to 2 decimal places.) 2016 2017 2018 Operating profit margin % % % Asset turnover Required 1 Required 2 Required 3 Required 4 Has Nucor's profitability changed over the three years? Has Nucor's profitability changed over the three years? Yes NoRequired 1 Required 2 Required 3 Required 4 Calculate the rate of return on common stockholders' equity for 2016, 2017, and 2018. (Do not round intermediate calculations. Round your answers to 2 decimal places.) 2016 2017 2018 Rate of return on common stockholders' equity % % % Required 1 Required 2 Required 3 Required 4 Calculate Nucor's ROA for 2016, 2017, and 2018. (Do not round intermediate calculations. Round your answers to 2 decimal places.) 2016 2017 2018 ROA % % %