The following bar graph shows the sales of books (in thousands) from 3 branches of a company in three consecutive years 2018, 2019 and 2020.
What is the ratio of the total sales of branch A for the year 2018 to the total sales of branch C for the year 2020?
1
1 ∶ 1
2
5 ∶ 1
3
4 ∶ 3
4
1 ∶ 5