Refer to the following mentioned data. Net Sales Cost of products sold Gross margin (In millions) 2017 2016 2015 $34,993 $30,873 $26.306 14,016 13,639 13.433 $20,977 $17,234 513,373 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 $1239 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 (.e., 5.000.000 should be entered as 5).) Cost of goods sold Gross profit