A 4-letter code word consists of letters X, Y, and Z. If the code includes all the three letters, how many such codes are possible?	Choose the correct choice from the following answers.
A) 36 B) 72 C) 48 D) 24 E) 18
Note that the correct answer to this question is 36, not 72.   X-XYZ can be arranged in 4!/2!=12 ways;   Y-XYZ can be arranged in 4!/2!=12 ways;   Z-XYZ can be arranged in 4!/2!=12 ways;   Total:  12+12+12= 
<gadget id="calculator"> 12+12+12</gadget>
<output>36</output>
36.   36nswer: 36.
<result>A</result>
A 4-letter code word consists of letters X, Y, and Z. If the code includes all the three letters, how many such codes are possible?