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'.

Example Input: 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
Example Output: b

Example Input: Problem: what is the value of 8 1 / 3 % of 600 + 37 ½ of 400 
Options: a ) 100 , b ) 300 , c ) 150 , d ) 200 , e ) 250
Example Output: d

Example Input: Problem: each of the 20 boxes in a certain shipment weighs either 10 pounds or 20 pounds , and the average ( arithmetic mean ) weight of the boxes in the shipment is 18 pounds . if the average weight of the boxes in the shipment is to be reduced to 16 pounds by removing some of the 20 - pound boxes , how many 20 - pound boxes must be removed ? 
Options: a ) 8 , b ) 10 , c ) 12 , d ) 14 , e ) 15
Example Output:
b