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: how many seconds will a train 100 meters long take to cross a bridge 160 meters long if the speed of the train is 36 kmph ? 
Options: a ) 26 , b ) 72 , c ) 25 , d ) 82 , e ) 27
Example Output: a

Example Input: Problem: a can do a piece of work in 8 days and b alone can do it in 12 days . how much time will both take to finish the work ? 
Options: a ) a ) 4.8 , b ) b ) 6.333 , c ) c ) 7.333 , d ) d ) 8.5 , e ) e ) 9
Example Output: a

Example Input: Problem: the radius of a semi circle is 7 cm then its perimeter is ? 
Options: a ) 32.8 , b ) 36 , c ) 32.1 , d ) 32.2 , e ) 32.9
Example Output:
b