Task: Question Answering
Input (English): Problem: car a runs at the speed of 50 km / hr and reaches its destination in 8 hours . car b runs at the speed of 70 km / h and reaches its destination in 4 hours . what is the ratio of distances covered by car a and car b ? 
Options: a ) 3 : 7 , b ) 4 : 9 , c ) 10 : 7 , d ) 5 : 7 , e ) 6 : 11
Output (English): c