In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Example Input: Problem: the ratio between the speeds of two trains is 7 : 8 . if the second train runs 400 km in 4 hours , what is the the speed of the first train ? 
Options: a ) 87.0 , b ) 87.5 , c ) 87.2 , d ) 87.1 , e ) 87.4
Example Output: b

Example Input: Problem: john and lewis leave city a for city b simultaneously at 6 a . m in the morning driving in two cars at speeds of 40 mph and 60 mph respectively . as soon as lewis reaches city b , he returns back to city a along the same route and meets john on the way back . if the distance between the two cities is 240 miles , how far from city a did john and lewis meet ? 
Options: a ) 150 miles , b ) 160 miles , c ) 140 miles , d ) 170 miles , e ) 200 miles
Example Output: b

Example Input: Problem: a can do a half of certain work in 70 days and b one third of the same in 35 days . they together will do the whole work in ? 
Options: a ) 1 / 65 , b ) 1 / 62 , c ) 1 / 63 , d ) 1 / 60 , e ) 1 / 61
Example Output:
d