The number of restaurants in a city increases each year.
• In 2005 there were 42 restaurants in the city.
• In 2009 there were 61 restaurants in the city.
What is the average rate of change from 2005 to 2009?
A. 4.75 restaurants per year
B. 3.80 restaurants per year
C. -3.80 restaurants per year
D. -4.75 restaurants per year