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 a boat at 10 kmph in still water and the speed of the stream is 8 kmph . what is then time taken to row a distance of 90 km down the stream ? 
Options: a ) 8 hrs , b ) 5 hrs , c ) 15 hrs , d ) 15 hrs , e ) 20 hrs
Example Output: b

Example Input: Problem: jim drove 768 miles of a 1200 miles journey . how many more miles does he need to drive to finish his journey ? 
Options: a ) 432 miles , b ) 651 miles , c ) 387 miles , d ) 954 miles , e ) 556 miles
Example Output: a

Example Input: Problem: the inner circumference of a circular race track , 14 m wide is 440 m . find the radius of the outer circle . 
Options: a ) 84 , b ) 12 , c ) 67 , d ) 28 , e ) 21
Example Output:
a