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: in a kilometer race , a beats b by 40 meters or 10 seconds . what time does a take to complete the race ? 
Options: a ) 290 sec , b ) 190 sec , c ) 199 sec , d ) 192 sec , e ) 240 sec
Example Output: e

Example Input: Problem: 20 beavers , working together in a constant pace , can build a dam in 18 hours . how many hours will it take 12 beavers that work at the same pace , to build the same dam ? 
Options: a ) 22 . , b ) 24 . , c ) 30 . , d ) 36 , e ) 38 .
Example Output: c

Example Input: Problem: a man crosses a 600 m long street in 5 minutes . what is his speed in km per hour ? 
Options: a ) 7 km / hr , b ) 7.2 km / hr , c ) 5.2 km / hr , d ) 10 km / hr , e ) 5 km / hr
Example Output:
b