Little help with permutations There are 4 letters $A, B, C, D$ with repetitions permitted. These letters are used in a a 3 letter code (the order is important).   


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*Question 1:
How many different 3 letter codes can be made? 

*Question 2:
If one code is chosen at random from the set of all possible codes, what is the probability it contains two A's and a D?    
Now I haven't done probability in a very long time but I believe this is just a standard permutation question? Would I be correct in saying that the first question is $4^3$? So there will be 64 different codes.

Hint: How many codes satisfying the condition that they include two A and one D are there? 
