x, y, and z are all unique numbers. If x is chosen randomly from the set {5, 6, 7, 8, 9, 10, 11} and y and z are chosen randomly from the set {20, 21, 22, 23}, what is the probability that x and y are prime and z is not?  Choose the correct option.
A) 1/5	B) 3/20	C) 1/7	D) 2/15	E) 3/28
P(x is prime) = 3/7   P(y is prime) = 1/4   If y is prime, then z is not prime since y and z are unique.   Then the probability is 3/7*1/4 = 3/28   The answer is 3/28.
<result>E</result>
x, y, and z are all unique numbers. If x is chosen randomly from the set {5, 6, 7, 8, 9, 10, 11} and y and z are chosen randomly from the set {20, 21, 22, 23}, what is the probability that x and y are prime and z is not?