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 train 284 m in length crosses a telegraph post in 18 seconds . the speed of the train is ? 
Options: a ) 77 kmph , b ) 55 kmph , c ) 57 kmph , d ) 58 kmph , e ) 76 kmph
Example Output: c

Example Input: Problem: convert 500 miles to km ? 
Options: a ) 600 km , b ) 700 km , c ) 800 km , d ) 900 km , e ) 1000 km
Example Output: c

Example Input: Problem: two trains each 150 m in length are running on the same parallel lines in opposite directions with the speed of 80 kmph and 70 kmph respectively . in what time will they cross each other completely ? 
Options: a ) 7.8 sec , b ) 7.2 sec , c ) 8.2 sec , d ) 6.2 sec , e ) 9.2 sec
Example Output:
b