Mayra buys a sweater for $20. The next month, the store increases the price of the sweater to $24. What is the percent increase in the price of the sweater?
A. 20% increase, because 24 over 20 equals X over 100.
B. 17% increase, because 4 over 24 equals X over 100.
C. 17% increase, because 20 over 24 equals X over 100.
D. 20% increase, because 4 over 20 equals X over 100.