M6-21. Using Inventory Analysis Tools AutoZone and O'Reilly are two competitors in the retail automotive parts industry. $ thousands AutoZone O'Reilly Average 2018 Inventory... $ 3,912,878 $3,101,572 2018 Sales... 11,221,077 9,536,428 2018 Cost of goods sold.... 5,247,331 4,496,462 Average 2017 Inventory.... $ 3,757,001 $2,894,388 2017 Sales.... 2017 Cost of goods sold.... 10,888,676 5,149,056 8,977,726 4,257,043 a. Use the information above to compute the companies' gross profit margin and days inventory out- standing for both years. b. Based on these two ratios, which company is more profitable selling its inventory? How has that changed from 2017 to 2018? c. Based on these two ratios, which company is more efficient with its inventory? How has that changed from 2017 to 2018?