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: if the wheel is 12 cm then the number of revolutions to cover a distance of 1240 cm is ? 
Options: a ) 11 , b ) 14 , c ) 16 , d ) 12 , e ) 19
Example Output: c

Example Input: Problem: a boat running downstream covers a distance of 12 km in 2 hours while for covering the same distance upstream , it takes 3 hours . what is the speed of the boat in still water ? 
Options: a ) 8 kmph , b ) 5 kmph , c ) 4 kmph , d ) 6 kmph , e ) 7 kmph
Example Output: b

Example Input: Problem: factory x ' s bulbs work for over 4000 hours in 59 % of cases , whereas factory y ' s bulbs work for over 4000 hours in 65 % of cases . it is known that factory x supplies 60 % of the total bulbs available . what is the chance that a purchased bulb will work for longer than 4000 hours ? 
Options: a ) 66.4 % , b ) 61.4 % , c ) 77.4 % , d ) 65 % , e ) 53.9 %
Example Output:
b