Multiple-choice questions on a test each have 5 possible answers, ...

[K@]

Multiple-choice questions on a test each have 5 possible answers, one of which is correct.
  Assume that you guess the answers to 5 such questions.
 
  a. Use the multiplication rule to find the probability that the first 2 guesses are wrong and
  the last 3 guesses are correct. That is, find P(WWCCC), 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 3
  correct answers, then find the probability for each entry in the list.
  c. Based on the preceding results, what is the probability of getting exactly 3 correct
  answers when 5 guesses are made?

Question 2

A study of the amount of time it takes a mechanic to rebuild the transmission for a 2005 Chevrolet
  Cavalier shows that the mean is 8.4 hours and the standard deviation is 1.8 hours.
 
  If 40 mechanics
  are randomly selected, find the probability that their mean rebuild time is less than 8.9 hours.
  A) 0.9589 B) 0.4276 C) 0.9608 D) 0.9756

[chem1s3]

Answer to Question 1

a. 0.00512
b. WWCCC
WCWCC
WCCWC
WCCCW
CWWCC
CWCWC
CWCCW
CCWWC
CCWCW
CCCWW
Each of the 10 arrangements has probability 0.00512
c. 0.0512

Answer to Question 2

C