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 overtakes two person who are walking in the same direction in which the train is going , at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10 seconds respectively . the length of the train is :
Options: a ) 45 m , b ) 50 m , c ) 54 m , d ) 72 m , e ) none of these
Example Output: b

Example Input: Problem: what is the least number of square tiles required to pave the floor of a room 11 m 50 cm long and 1 m 50 cm broad ?
Options: a ) 724 , b ) 804 , c ) 69 , d ) 844 , e ) none
Example Output: c

Example Input: Problem: in an intercollegiate competition that lasted for 3 days , 150 students took part on day 1 , 110 on day 2 and 140 on day 3 . if 75 took part on day 1 and day 2 and 25 took part on day 2 and day 3 and 15 took part on all three days , how many students took part only on day 2 ?
Options: a ) 50 , b ) 35 , c ) 45 , d ) 25 , e ) 60
Example Output:
d