How many four-digit personal identification numbers (PIN) are possible if the PIN cannot begin or end with a 0 and the PIN must be an even number?

The first digit can be any of the 9 nonzero digits. The last digit must be even and cannot be 0, so it has 4 choices: 2, 4, 6, or 8. Each of the two middle digits has 10 choices, giving 9 × 10 × 10 × 4 = 3,600 possible PINs. The correct choice is 3,600.

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