A teacher has a bag of marbles. There are 6 red, 6 blue, 8 green, 7 purple, and 8 yellow marbles in the bag. As the students enter the classroom, they draw a marble and keep it. If the first student in the room draws a yellow, and the second draws a purple, what is the probability that the third student will draw a yellow also? A) 33
B) 20
C) 21