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: john traveled 80 % of the way from yellow - town to green - fields by train at an average speed of 80 miles per hour . the rest of the way john traveled by car at an average speed of v miles per hour . if the average speed for the entire trip was 60 miles per hour , what is v in miles per hour ? 
Options: a ) 30 , b ) 40 , c ) 50 , d ) 55 , e ) 70
Example Output: a

Example Input: Problem: 63 men working 8 hours per day dig 30 m deep . how many extra men should be put to dig to a depth of 50 m working 6 hours per day ? 
Options: a ) a ) 87 , b ) b ) 77 , c ) c ) 66 , d ) d ) 55 , e ) e ) 97
Example Output: b

Example Input: Problem: a and b complete a work in 10 days . a alone can do it in 40 days . if both together can do the work in how many days ? 
Options: a ) 1.0875 days , b ) 0.125 days , c ) 0.0675 days , d ) 0.0875 days , e ) 0.0775 days
Example Output:
b