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'.

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


[Q]: Problem: for what values of k will the pair of equations 4 ( 3 x + 4 y ) = 48 and kx + 12 y = 30 does not have a unique solution ? 
Options: a ) 12 , b ) 9 , c ) 3 , d ) 7.5 , e ) 2.5
[A]: b


[Q]: Problem: 4 / 15 of 5 / 7 of a number is greater than 4 / 9 of 2 / 5 of the same number by 8 . what is half of that number ? 
Options: a ) 305 , b ) 315 , c ) 345 , d ) 325 , e ) 335
[A]:
b