From 2012 to 2013, Berry Barn reported that its Net Sales increased from $300,000 to $400,000, and

Question:

From 2012 to 2013, Berry Barn 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.