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

Input: Consider Input: Problem: two vessels contains equal number of mixtures milk and water in the ratio 7 : 2 and 8 : 1 . both the mixtures are now mixed thoroughly . find the ratio of milk to water in the new mixture so obtained ? 
Options: a ) 1 : 3 , b ) 9 : 13 , c ) 5 : 1 , d ) 11 : 3 , e ) 15 : 4

Output: c


Input: Consider Input: Problem: a student committee on academic integrity has 90 ways to select a president and vice president from a group of candidates . the same person can not be both president and vice president . how many candidates are there ? 
Options: a ) 7 , b ) 8 , c ) 9 , d ) 10 , e ) 11

Output: d


Input: Consider Input: Problem: in a group of 12 engineers , 4 engineers have a phd degree ; the others have only an ms or bs degree . a team of 4 engineers is to be chosen which must have at least 1 engineer with a phd , how many different teams can be chosen ? 
Options: a ) 495 , b ) 70 , c ) 245 , d ) 425 , e ) 555


Output: d