Firm a Notices That Firm B Is Making a Profit

Multiple Choice

Firm A notices that Firm B is making a profit by producing footballs.There is nothing stopping Firm A from entering the football market,so it does.Holding all else constant,the number of firms in the market will

A) increase,causing demand to increase.
B) increase,causing the supply to shift down.
C) decrease,causing the supply to decrease.
D) decrease,causing the supply to increase.
E) increase,causing the supply to increase.