Probability question:

A student takes a 19-question, multiple choice exam with three choices for each question and guesses on each question. Find the probability of guessing exactly 8 out of 19 correctly.

I used 19C8 so n=19 x =8 p=.33 and q=.67 but I can't come up with any of the answers that are on my homework.

I am a beginning statistics/probability student. Showing your work would be helpful to me so I can learn how to do this stuff. Thanks for any help you are able to give, I appreciate it!