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: two trains 140 m and 160 m long run at the speed of 60 km / hr and 40 km / hr respectively in opposite directions on parallel tracks . the time ( in seconds ) which they take to cross each other , is :
Options: a ) 9 , b ) 9.6 , c ) 10 , d ) 10.8 , e ) 7
Example Output: d

Example Input: Problem: a can finish a work in 18 days and b can do same work in half the time taken by a . then working together , what part of same work they can finish in a day
Options: a ) 1 \ 5 , b ) 1 \ 6 , c ) 1 \ 7 , d ) 1 \ 8 , e ) 1 \ 9
Example Output: b

Example Input: Problem: a courtyard is 25 meter long and 16 meter board is to be paved with bricks of dimensions 20 cm by 10 cm . the total number of bricks required is :
Options: a ) 16000 , b ) 18000 , c ) 20000 , d ) 22000 , e ) none of these
Example Output:
c