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: the sum of ages of 5 children born at the intervals of 3 years each is 80 years . what is the age of the youngest child ? 
Options: a ) 3 years , b ) 4 years , c ) 6 years , d ) 7 years , e ) 10 years
[A]: e


[Q]: Problem: √ ( 36 ) ^ 2 
Options: a ) 6 , b ) 14 , c ) 36 , d ) 21 , e ) none of these
[A]: c


[Q]: Problem: at a certain food stand , the price of each apple is 40 ¢ and the price of each orange is 60 ¢ . mary selects a total of 10 apples and oranges from the food stand , and the average ( arithmetic mean ) price of the 10 pieces of fruit is 54 ¢ . how many oranges must mary put back so that the average price of the pieces of fruit that she keeps is 50 ¢ ? 
Options: a ) 1 , b ) 2 , c ) 3 , d ) 4 , e ) 5
[A]:
d