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'.
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Question: 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

Answer: a


Question: Problem: 11 + 12 + 13 + . . . 51 + 52 = ? 
Options: a ) 1361 , b ) 1362 , c ) 1323 , d ) 1364 , e ) 1365

Answer: c


Question: Problem: each of the positive integers a and c is a 4 - digit integer . if each of the digits 0 through 9 appears in one of these 3 integers , what is the maximum possible value of the sum of a and c ? 
Options: a ) 18695 , b ) 18325 , c ) 18365 , d ) 18395 , e ) 18485

Answer:
d