Probability Problem

Multiple-choice questions on a test each have 6 possible answers, one of which is correct. Assume that you guess the answers to 4 such questions. 

a. Use the multiplication rule to find the probability that the first two guesses are wrong and the third and fourth guesses are correct. That is, find P(WWCC), where C denotes a correct answer and W denotes a wrong answer. 

b. Make a complete list of the different possible arrangements of 2 wrong answers and 2 correct answers, and then find the probability for each entry in the list. 

c. Based on the preceding results, what is the probability of getting exactly 2 correct answers when 4 guesses are made?