Question 1092054
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In 12*11*10*9*8 = 95040 ways.


Anyone of 12           amino acid in the 1-st position;
Anyone of 11 remaining amino acid in the 2-nd position;
Anyone of 10 remaining amino acid in the 3-rd position;
Anyone of  9 remaining amino acid in the 4-th position;
Anyone of  8 remaining amino acid in the 5-nd position.


In all, you get this quantity,  {{{12P[5]}}} = 12*11*10*9*8 = 95040 ways.
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Under the assumption that this logic really works in this situation.