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: what is the minimum percentage increase in the mean of set f { - 4 , - 1 , 0 , 6 , 9 } if its two smallest elements are replaced with two different primes ? 
Options: a ) 25 % , b ) 50 % , c ) 75 % , d ) 100 % , e ) 200 %
[EX A]: d

[EX Q]: Problem: the least number , which when divided by 12 , 31 , 20 and 54 leaves in each case a remainder of 8 is : 
Options: a ) 448 , b ) 488 , c ) 16748 , d ) 548 , e ) 560
[EX A]: c

[EX Q]: Problem: a manufacturer produces a certain men ' s athletic shoe in integer sizes from 8 to 17 . for this particular shoe , each unit increase in size corresponds to a 1 / 5 - inch increase in the length of the shoe . if the largest size of this shoe is 40 % longer than the smallest size , how long , in inches , is the shoe in size 15 ? 
Options: a ) 5.4 , b ) 5.9 , c ) 6.3 , d ) 6.7 , e ) 7.5
[EX A]:
b