A 4-letter code word consists of letters L, M, AND N. If the code includes all the three letters, how many such codes are possible?
Choose the correct answer.
A) 72
B) 36
C) 24
D) 44
E) 22
Note that the correct answer to this question is 36, not 72.   L-LMN can be arranged in 4!/2!=12 ways;   M-LMN can be arranged in 4!/2!=12 ways;   N-LMN can be arranged in 4!/2!=12 ways;   Total:  12+12+12= 
<gadget id="calculator"> 12+12+12</gadget>
<output>36</output>
36.   Answer: 36
<result>B</result>
A 4-letter code word consists of letters L, M, AND N. If the code includes all the three letters, how many such codes are possible?