From 2013 to 2014, Mechanic International reported that its Net Sales increased from $300,000 to $400,000, and

Question:

From 2013 to 2014, Mechanic International reported that its Net Sales increased from $300,000 to $400,000, and its Gross Profit increased from $90,000 to $130,000. Was the Gross Profit increase caused by (a) an increase in sales volume only, (b) an increase in gross profit per sale only, or (c) a combination of both? Explain your answer.