Study the following bar graph that shows the number of students enrolled for different courses in institutes A and B during 5 years, and answer the question that follows.
What is the ratio of the total number of students enrolled in A during 2015 and 2018 to that of students enrolled in B during 2014 and 2015?
1
17 ∶ 13
2
13 ∶ 17
3
13 ∶ 12
4
12 ∶ 13