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: a and b can do a work in 25 days and 10 days respectively . a starts the work and b joins him after 2 days . in how many days can they complete the remaining work ?
Options: a ) 4.28 days , b ) 4.38 days , c ) 5.28 days , d ) 6.28 days , e ) 2.28 days
Example Output: a

Example Input: Problem: the sum of three consecutive even numbers is 63 . find the middle number of the three ?
Options: a ) 14 , b ) 23 , c ) 25 , d ) 29 , e ) 21
Example Output: e

Example Input: Problem: a train traveling at 100 kmph overtakes a motorbike traveling at 64 kmph in 40 seconds . what is the length of the train in meters ?
Options: a ) 400 meters , b ) 1111 meters , c ) 1777 meters , d ) 1822 meters , e ) none of these
Example Output:
a