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: set s contains exactly 10 numbers and has an average ( arithmetic mean ) of 6.2 . if one of the numbers in set s is increased by 8 , while all other numbers remain the same , what is the new average of set s ? 
Options: a ) 6.6 , b ) 6.7 , c ) 6.8 , d ) 7.0 , e ) 6.9
Example Output: d

Example Input: Problem: if ( a - b - c + d = 13 ) and ( a + b - c - d = 9 ) , what is the value of ( b - d ) ^ 2 ? 
Options: a ) 4 . , b ) 8 . , c ) 12 . , d ) 16 . , e ) 64 .
Example Output: a

Example Input: Problem: a rainstorm increased the amount of water stored in state j reservoirs from 160 billion gallons to 200 billion gallons . if the storm increased the amount of water in the reservoirs to 40 percent of total capacity , approximately how many billion gallons of water were the reservoirs short of total capacity prior to the storm ? 
Options: a ) 260 , b ) 280 , c ) 325 , d ) 340 , e ) 355
Example Output:
d