You will be given a definition of a task first, then some input of the task.
In this task, you need to provide the correct option for a given problem on probability from the provided options.

Problem: an urn contains 5 red , 6 blue and 8 green balls . 4 balls are randomly selected from the urn , find the probability that the drawn ball are 1 blue and 3 red ? 
Options: a ) 1 / 969 , b ) 2 / 969 , c ) 4 / 969 , d ) 5 / 323 , e ) 21 / 789
Output:
d