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

Problem: the cost of 3 pens and 5 pencils is rs . 260 . also the cost of one pen and one pencil is in the ratio of 5 : 1 respectively . what is the cost of one dozen pens ? 
Options: a ) rs . 200 , b ) rs . 250 , c ) rs . 300 , d ) rs . 780 , e ) none of these
d

Problem: the compound ratio of 2 / 3 , 6 / 7 , 1 / 3 and 1 / 8 is given by ? 
Options: a ) 1 / 49 , b ) 1 / 42 , c ) 1 / 09 , d ) 1 / 77 , e ) 1 / 12
b

Problem: in a class of 39 students 26 play football and play 20 long tennis , if 17 play above , many play neither ? 
Options: a ) 6 , b ) 8 , c ) 10 , d ) 12 , e ) 14

c