Task: Question Answering
Input (English): Problem: two trains , a and b , started simultaneously from opposite ends of a 75 - mile route and traveled toward each other on parallel tracks . train a , traveling at a constant rate , completed the 75 - mile trip in 3 hours ; train b , traveling at a constant rate , completed the 75 - mile trip in 2 hours . how many miles had train a traveled when it met train b ? 
Options: a ) 20 , b ) 22.5 , c ) 30 , d ) 37.5 , e ) 45
Output (English): c