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 start walking from a place at a uniform speed of 4 kmph in a particular direction . after half an hour , b starts from the same place and walks in the same direction as a at a uniform speed and overtakes a after 1 hour 48 minutes . find the speed of b . 
Options: a ) 4.7 kmph , b ) 4.6 kmph , c ) 4 kmph , d ) 7 kmph , e ) 5.3 kmph
Example Output: b

Example Input: Problem: a train 280 m long , running with a speed of 72 km / hr will pass a tree in 
Options: a ) 14 sec , b ) 15 sec , c ) 16 sec , d ) 20 sec , e ) none
Example Output: a

Example Input: Problem: a and b can do a piece of work in 40 days and 50 days respectively . they work together for 10 days and b leaves . in how many days the whole work is completed ? 
Options: a ) 28 days , b ) 60 days , c ) 20 days , d ) 30 days , e ) 40 days
Example Output:
a