The bar graph given below shows the sales of books (in thousand number) from six branches of a publishing company during two consecutive years 2000 and 2001.



What is the ratio of the total sales of branch B2 for both years to the total sales of branch B4 for both years?

1. A
   $2:3$
2. B
   $3:5$
3. C
   $4:5$
4. D
   $7:9$