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 two of the 4 expressions x + y , x + 5 y , x - y , and 5 x - y are chosen at random , what is the probability w that their product will be of the form of x ^ 2 - ( by ) ^ 2 , where b is an integer ? 
Options: a ) 1 / 2 , b ) 1 / 3 , c ) 1 / 4 , d ) 1 / 5 , e ) w = 1 / 6
[A]: e


[Q]: Problem: the sum of the first 50 positive even integers is 2550 . what is the sum w of even integers from 102 to 200 inclusive ? 
Options: a ) 5100 , b ) 7550 , c ) 10100 , d ) 15500 , e ) 20100
[A]: b


[Q]: Problem: the ages of two persons differ by 16 years . if 6 years ago , the elder one be 3 times as old as the younger one , find their present ages . 
Options: a ) 10 years and 18 years , b ) 18 years and 26 years , c ) 20 years and 28 years , d ) 14 years and 30 years , e ) 16 years and 25 years
[A]:
d