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: pure milk costs 3.60 per litre . a milkman adds water to 25 litres of pure milk and sells the mixture at 3 per litre . how many litres of water does he add ? 
Options: a ) 2 litres , b ) 5 litres , c ) 7 litres , d ) 11 litres , e ) none of these

A: b
****
Q: Problem: in a group of ducks and cows , the total number of legs are 22 more than twice the no . of heads . find the total no . of buffaloes . 
Options: a ) 11 , b ) 12 , c ) 13 , d ) 15 , e ) 16

A: a
****
Q: Problem: the product of a and b is equal to 11 more than twice the sum of a and b . if b = 7 , what is the value of b - a ? 
Options: a ) 2 , b ) 5 , c ) 7 , d ) 24 , e ) 35

A:
a
****