M6-16 Interpreting Changes in Gross Profit Percentage Luxottica Group, the Italian company that sells Ray Ban and Oakley sunglasses, reported net sales of 8.8 billion in 2015 and 7.6 billion in 2014. Gross profit increased from 5.1 billion in 2014 to 6.0 billion in 2015. Was the increase in gross profit caused by (a) an increase in gross profit per sale, (b) an increase in sales volume, or (c) a combination of (a) and (b)