Task: Question Answering
Input (English): Problem: lionel left his house and walked towards walt ' s house , 48 miles away . two hours later , walt left his house and ran towards lionel ' s house . if lionel ' s speed was 3 miles per hour and walt ' s 4 miles per hour , how many miles had lionel walked when he met walt ? 
Options: a ) 12 , b ) 16 , c ) 20 , d ) 24 , e ) 28
Output (English): d