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: calculate the speed of a boat in still water ( in km / hr ) if in one hour , the boat goes 10 km / hr downstream and 4 km / hr upstream . 
Options: a ) 7 kmph , b ) 8 kmph , c ) 9 kmph , d ) 7 kmph , e ) 6 kmph
Example Output: a

Example Input: Problem: 6 bells commence tolling together and toll at the intervals of 24 , 68 , 1012 seconds resp . in 60 minutes how many times they will toll together . 
Options: a ) 15 , b ) 16 , c ) 30 , d ) 31 , e ) none of these
Example Output: d

Example Input: Problem: a can run 224 metre in 28 seconds and b in 32 seconds . by what distance a beat b ? 
Options: a ) 38 metre , b ) 28 metre , c ) 23 metre , d ) 15 metre , e ) 28 metre
Example Output:
b