Task: Question Answering
Input (English): Problem: a train traveled the first d miles of its journey it an average speed of 40 miles per hour , the next d miles of its journey at an average speed of y miles per hour , and the final d miles of its journey at an average speed of 160 miles per hour . if the train ’ s average speed over the total distance was 96 miles per hour , what is the value of y ? 
Options: a ) 68 , b ) 84 , c ) 100 , d ) 120 , e ) 135
Output (English): c