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'.

Ex Input:
Problem: if 45 - [ 28 - { 37 - ( 15 - * ) } ] = 59 , then * is equal to : 
Options: a ) - 29 , b ) - 19 , c ) 20 , d ) 29 , e ) 39

Ex Output:
c


Ex Input:
Problem: how many odd 3 - digit integers greater than 800 are there such that all their digits are different ? 
Options: a ) 40 , b ) 56 , c ) 72 , d ) 81 , e ) 104

Ex Output:
c


Ex Input:
Problem: if a 10 percent deposit that has been paid toward the purchase of a certain product is $ 80 , how much more remains to be paid ? 
Options: a ) $ 640 , b ) $ 680 , c ) $ 720 , d ) $ 760 , e ) $ 800

Ex Output:

c