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'.

Input: Consider Input: Problem: the unit digit in the product ( 891 * 781 * 912 * 463 ) is :
Options: a ) 2 , b ) 5 , c ) 6 , d ) 8 , e ) 10

Output: c

Input: Consider Input: Problem: 120 + 520 5.00 = ?
Options: a ) 100 , b ) 150 , c ) 120 , d ) 520 , e ) none

Output: e

Input: Consider Input: Problem: company x provides bottled water to its employees in 5 liter bottles , $ 2 each . at least how many 5 l bottles must company x buy monthly , so that new contract with $ 100 fixed monthly rate and $ 1 for 10 l bottle each paid off ? ( assume that no other costs apply )
Options: a ) 121 , b ) 125 , c ) 132 , d ) 134 , e ) 138
Output: d