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 average marks of a class of 30 students is 40 and that of another class of 50 students is 60 . find the average marks of all the students ? 
Options: a ) 82.5 , b ) 52.9 , c ) 52.2 , d ) 52.5 , e ) 52.7
[A]: d


[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: if 3 ^ x * 4 ^ y = 4 , 782,969 and x – y = 14 , then x = ? 
Options: a ) 10 , b ) 11 , c ) 12 , d ) 13 , e ) 14
[A]:
e