Refer to the following mentioned data. (In millions) 2016 2017 2015 Net sales $34,732 $30,512 $26,578 Cost of products 14,958 13,812 13,944 sold Gross margin $19,774 $16, 700 $12,634 Required: a. Calculate the gross profit ratio for each of the past three years. (Round your answers to 2 decimal places.) 2017 2016 56.93 % 54.73 % 2015 47.54% b. Assume that Campbell's net sales for the first four months of 2018 totaled $12.89 billion. Calculate an estimated cost of goods sold and gross profit for the four months, using the gross profit ratio for 2017. (Round intermediate calculations to 2 decimal places. Enter your answers in millions rounded to nearest whole number (i.e., 5,000,000 should be entered as 5).) Cost of goods sold million million Gross profit