Task: Question Answering
Input (English): Problem: two friends decide to get together ; so they start riding bikes towards each other . they plan to meet halfway . each is riding at 6 mph . they live 36 miles apart . one of them has a pet carrier pigeon and it starts flying the instant the friends start traveling . the pigeon flies back and forth at 21 mph between the 2 friends until the friends meet . how many miles does the pigeon travel ? 
Options: a ) 54 , b ) 66 , c ) 68 , d ) 60 , e ) 63
Output (English): e