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Answer. different licence plates.
Solution
10 different digits are possible in the very left-most position, which gives 10 options.
10 different digits are possible in the next position, which gives 10 options.
10 different digits are possible in the third position, which gives 10 options.
10 different digits are possible in the fourth position, which gives 10 options.
Any of 26 letters can occupy the 5-th position, which gives 26 options.
Any of 26 letters can occupy the 6-th position, which gives 26 options.
When you multiply all options (that are independent !), you will get the answer.