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 man can row 4 kmph in still water . when the river is running at 1.8 kmph , it takes him 1 hour to row to a place and black . what is the total distance traveled by the man ? 
Options: a ) 7.13 , b ) 6.19 , c ) 4.12 , d ) 3.19 , e ) 4.21
Example Output: b

Example Input: Problem: a can finish a piece of work in 12 days . b can do it in 20 days . they work together for 9 days and then a goes away . in how many days will b finish the work ? 
Options: a ) 6 days , b ) 4 days , c ) 5 days , d ) 3 days , e ) 7 days
Example Output: c

Example Input: Problem: a pump can fill a tank with water in 4 hours . because of a leak , it took 20 hours to fill the tank . the leak can drain all the water of the tank in ? 
Options: a ) 1 , b ) 3 , c ) 5 , d ) 4 , e ) 2
Example Output:
c