Refer to the following mentioned data. Net sales Cost of products sold Gross margin (In millions) 2017 2016 2015 $34, 159 $30,602 $26,968 14,499 13,617 13,243 $19,660 $16,985 $13,725 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 $12.19 billion. Calculate an estimated cost of goods sold and gross profit for the four months, using the gross profit ratio for 2017. (Round inter ions 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