Todd,

You raise a very good point. But if we can select only from the digits 1, 2, 3, 4, 5, 6, 7, and 8, then we get a number of possible combinations that is not among the answer choices.

With this restricted set, the first space, which has to be a prime, can only be 2, 3, 5, or 7. That's

4 choices. The second space has all

8 possible digits. The third space has

8 again. The fourth space could be 2, 4, 6, or 8.

4 Choices.

4 *

8 *

8 *

4 =

1024. That number is not offered.

So we have to assume, even if it is contrary to the test's convention, that we are allowed to use 0 and 9.

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