Fortune Brands Home & Security, Inc. sells Master Lock padlocks. It reported an increase in net sales from $4.6 billion in 2011 to $4.9 billion in 2012, and an increase in gross profit from $1.4 billion in 2011 to $1.6 billion in 2012.

a. Calculate each year's gross profit percentage. (Round your answer to 1 decimal place.)

Gross Profit Percentage 2012 % 2011 %

b. Determine whether the change in gross profit was cause by.

an increase in gross profit per sale. an increase in sale volume. an increase in gross profit per sale and sales volume.