In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Example Input: Problem: 10 camels cost as much as 24 horses , 16 horses cost as much as 4 oxen and 6 oxen as much as 4 elephants . if the cost of 10 elephants is rs . 120000 , find the cost of a camel ? 
Options: a ) s . 9800 , b ) s . 3800 , c ) s . 9800 , d ) s . 4800 , e ) s . 6880
Example Output: d

Example Input: Problem: if n is an integer , f ( n ) = f ( n - 1 ) - n and f ( 4 ) = 14 . what is the value of f ( 6 ) ? 
Options: a ) 3 , b ) 0 , c ) 1 , d ) 2 , e ) 4
Example Output: a

Example Input: Problem: molly ' s age in 18 years will be 5 times her age 6 years ago . what is molly ' s present age ? 
Options: a ) 8 , b ) 9 , c ) 10 , d ) 12 , e ) 14
Example Output:
d