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: find the length of the wire required to go 15 times round a square field containing 69696 m 2 . 
Options: a ) 15840 , b ) 15848 , c ) 15828 , d ) 27892 , e ) 22892
Example Output: a

Example Input: Problem: mike drives his new corvette from san francisco to las vegas , a journey of 640 miles . he drives the first half of the trip at an average rate of 80 miles per hour , but has to slow down for the second half of his journey . if the second half of the trip takes him 200 percent longer than the first half , what is his average rate j in miles per hour for the entire trip ? 
Options: a ) 26.7 , b ) j = 30.0 , c ) j = 40.0 , d ) j = 53.3 , e ) 60.0
Example Output: c

Example Input: Problem: a man swims downstream 51 km and upstream 18 km taking 3 hours each time , what is the speed of the man in still water ? 
Options: a ) 2 , b ) 8.5 , c ) 9.5 , d ) 6.5 , e ) 11.5
Example Output:
e