A suitcase lock has 4 dials with the digits $0, 1, 2,..., 9$ on each. How many different settings are possible if all four digits have to be different?
Question:
A suitcase lock has 4 dials with the digits $0, 1, 2,..., 9$ on each. How many different settings are possible if all four digits have to be different?
Answer:
Let's think step by step.

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A suitcase lock has 4 dials with the digits $0, 1, 2,..., 9$ on each. How many different settings are possible if all four digits have to be different?
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