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 train 300 m long takes 9 sec to cross a man walking at 3 kmph in a direction opposite to that of the train . find the speed of the train ? 
Options: a ) 100 kmph , b ) 90 kmph , c ) 120 kmph , d ) 117 kmph , e ) 125 kmph
Example Output: d

Example Input: Problem: the lcm of two numbers is 2310 and hcf is 83 . if one of the numbers is 210 . then what is the other number ? 
Options: a ) 913 , b ) 825 , c ) 330 , d ) 582 , e ) 465
Example Output: a

Example Input: Problem: a can complete a project in 20 days and b can complete the same project in 30 days . if a and b start working on the project together and a quits 10 days before the project is completed , in how many days will the project be completed ? 
Options: a ) 18 days , b ) 27 days , c ) 26.67 days , d ) 16 days , e ) 12 days
Example Output:
a