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: if 213 × 16 = 3408 , then 16 × 21.3 is equal to : 
Options: a ) 0.3408 , b ) 3.408 , c ) 34.08 , d ) 340.8 , e ) none of these
[A]: d


[Q]: Problem: jacob is 39 years old . he is 3 times as old as his brother . how old will jacob be when he is twice as old ? 
Options: a ) 63 , b ) 64 , c ) 65 , d ) 76 , e ) 67
[A]: c


[Q]: Problem: the product of a and b is equal to 10 more than twice the sum of a and b . if b = 9 , what is the value of b - a ? 
Options: a ) 2 , b ) 5 , c ) 7 , d ) 24 , e ) 35
[A]:
b