Find the Indicated Probability $\frac { 1 } { 13 }$

Find the indicated probability. Round your answer to 6 decimal places when necessary.
-A bag contains 6 red marbles, 3 blue marbles, and 7 green marbles. If a marble is randomly selected from the bag, what is the probability that it is blue?

A) $\frac { 1 } { 13 }$
B) $\frac { 1 } { 3 }$
C) $\frac { 1 } { 7 }$
D) $\frac { 3 } { 16 }$