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'.

[EX 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
[EX A]: e

[EX Q]: Problem: when leo imported a certain item , he paid a 7 percent import tax on the portion of the total value of the item in excess of $ 1000 . if the amount of the import tax that leo paid was $ 87.50 , what was the total value of the item ? 
Options: a ) $ 1600 , b ) $ 1850 , c ) $ 2250 , d ) $ 2400 , e ) $ 2750
[EX A]: c

[EX Q]: Problem: the average marks of a class of 22 students is 40 and that of another class of 28 students is 60 . find the average marks of all the students ? 
Options: a ) 51.2 , b ) 59.5 , c ) 52.8 , d ) 52.5 , e ) 52.1
[EX A]:
a