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

Problem: teas worth rs . 126 per kg and rs . 135 per kg are mixed with a third variety in the ratio 1 : 1 : 2 . if the mixture is worth rs 156 per kg , the price of the third variety per kg will be ? 
Options: a ) rs . 147.50 , b ) rs . 785.50 , c ) rs . 178.50 , d ) rs . 258.50 , e ) none of these
c

Problem: the ratio between the present age of p and q is 6 : 7 . if q is 4 years old than p , what will be the ratio of the ages of p and q after 4 years ? 
Options: a ) 8 : 7 , b ) 7 : 8 , c ) 8 : 6 , d ) 6 : 7 , e ) 6 : 8
a

Problem: find the number of different prime factors of 441 
Options: a ) 4 , b ) 2 , c ) 3 , d ) 5 , e ) 6

b