Net sales Cost of products sold Gross margin (In millions) 2017 2016 2015 $34,880 $30,828 $26,567 14,517 13, 246 13,144 $20,363 $17,582 $13,423 Required: a. Calculate the gross profit ratio for each of the past three years. (Round your answers to 2 decimal places.) 2017 2016 2015 % % % b. Assume that Campbell's net sales for the first four months of 2018 totaled $12.39 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 Gross profit million million