Question 1118401
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You have three responses already to your question.<br>
The first one assumes the "digits" can't be repeated.<br>
The second one suggests that answer might not be right because your statement of the problem did not specify whether or not repetition is allowed.<br>
The third gives a possible answer based on the guess that repetition is allowed, which, without any direction one way or another, would be my interpretation.<br>
The third tutor also pointed out a bigger problem with your statement of the problem, which says you have 20 choices for each "digit" -- a problem which the other two tutors appear to have overlooked.  In base 10 (which I assume you are using, since no other base was specified), there are only 10 digits to choose from.<br>
The bottom line is that you wasted your time and the time of several tutors here by not formulating your problem clearly.<br>
When you are requesting help with a problem, it would be polite to take the time to make sure you have stated the problem correctly and clearly.