How many unique codes with this pattern? If I have a string of 4 chars, composed by 2 alphabetic chars and 2 numeric chars
Expamples:
AD98
CB77
HG47
HH33
The possible alphatic chars are:
A B C D E F G H K L M N P Q R S T U V X Y Z
The possibile numeric chars are:
2 3 4 5 6 7 8 9
How many unique codes are possibile?

If you allow repetitions, then it's $22^2\times 8^2$, without $22\times 21\times 8 \times 7$.
