Selected data from the September 30, 2017, and September 24, 2016, consolidated balance sheets and income statements for the years then ended for Apple Inc. follow. All amounts are reported in millions. Net sales 2017 $229,234 Cost of sales Research and development expenses Selling, general, and administrative expenses Operating income Other income, net Provision for income taxes Net income 2016 $215,639 141,048 131,376 11,581 10,045 15,261 14,194 ? ? ? 1,348 15,738 ? $ 48,351 $ 45,687 Required: a. Calculate the amount of Apple's gross profit for each year. Has gross profit as a percentage of sales changed significantly during the past year? b. Calculate the amount of Apple's operating income for each year. Has operating income as a percentage of sales changed significantly during the past year? c. After completing requirements a and b, calculate the other missing amounts for each year. Indicate the financial statement effect.