You will be given a definition of a task first, then some input of the task.
In this task, you need to provide the correct option for a given problem from the provided options.

Problem: in a certain school , the ratio of boys to girls is 5 to 13 . if there are 64 more girls than boys , how many boys are there ? 
Options: a ) 27 , b ) 40 , c ) 45 , d ) 72 , e ) 117
Output:
b