Instructions: In this task, you need to provide the correct option for a given problem from the provided options.
Input: Problem: if the ratio of a to b is 7 to 3 and the ratio of b to c is 1 to 5 , what is the ratio of a to c ? 
Options: a ) 4 / 15 , b ) 1 / 3 , c ) 2 / 5 , d ) 4 / 5 , e ) 7 / 15
Output:
e