In this task, you need to provide the correct option for a given problem from the provided options.

Example Input: Problem: a can contains a mixture of liquids a and b is the ratio 7 : 5 . when 3 litres of mixture are drawn off and the can is filled with b , the ratio of a and b becomes 7 : 9 . how many liter of liquid a was contained by the can initially ?
Options: a ) 7 , b ) 10 , c ) 12 , d ) 14 , e ) 16
Example Output: a

Example Input: Problem: the weights of one liter vegetable ghee packet of two brands ' a ' and ' b ' are 900 gm and 850 gm respectively . if they are mixed in the ratio of 3 : 2 by volumes to form a mixture of 4 liters , what is the weight ( in kg ) of the mixture ?
Options: a ) 3.84 , b ) 1.75 , c ) 3.52 , d ) 2.72 , e ) none of these
Example Output: c

Example Input: Problem: there are 399 doctors and nurses in a hospital . if the ratio of the doctors to the nurses is 8 : 11 , then how many nurses are there in the hospital ?
Options: a ) 152 , b ) 209 , c ) 57 , d ) 231 , e ) 181
Example Output:
d