First establish how many choices we have at each position:
1. "First five letters of the alphabet" --> 5 possibilities
2. "with no repeats" --> 4 possibilities (5 minus whatever was in spot 1)Ā
3. "digits 0 through 9" --> 10 possibilitiesĀ
4. "with repeats possible" --> 10 possibilitiesĀ
5. "with repeats possible" --> 10 possibilitiesĀ
Then we can calculate the total number of permutations by multiplying the the number of possibilities for each slot one after another:
[tex] 5 \times 4 \times 10 \times 10 \times 10 = 20,000 [/tex]