x, y, and z are all unique numbers. if x is chosen randomly from the set { 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 choice from the following answers:
A) 1 / 5 B) 3 / 20 C) 1 / 8 D) 3 / 10 E) 1 / 10
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/2) * (1/4)</gadget>
<output>1/8 = around 0.125</output>

<result>C</result>
x, y, and z are all unique numbers. if x is chosen randomly from the set { 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?
multiply(divide(const_1, const_2), divide(const_1, const_4))
p ( x is prime ) = 1 / 2 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 1 / 2 * 1 / 4 = 1 / 8 the answer is c .