Given the task definition and input, reply with output. In this task, you need to provide the correct option for a given problem on probability from the provided options.

Problem: in 15 year ’ s time the combined age of my 4 brothers will be 107 . what will it be in the 6 year ’ s time ? 
Options: a ) 61 , b ) 78 , c ) 71 , d ) 68 , e ) 94

c