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'.

Problem: a club wants to mix 20 pounds of candy worth $ 8.00 per pound with candy worth $ 5.00 per pound to reduce the cost of the mixture to $ 6.00 per pound . how many pounds of the $ 5.00 per pound candy should be used ? 
Options: a ) 20 , b ) 30 , c ) 40 , d ) 50 , e ) 60
c

Problem: each child has 6 crayons and 12 apples . if there are 12 children , how many crayons are there in total ? 
Options: a ) 22 , b ) 65 , c ) 72 , d ) 78 , e ) 90
c

Problem: what is the greatest prime factor of 5 ^ 6 - 1 ? 
Options: a ) 29 , b ) 31 , c ) 37 , d ) 41 , e ) 43

b