Answer:
175,760,000
Explanation:
This is the counting principle.
There are 7 positions. Multiply the number of possible characters in each position.
_ × _ × _ × _ × _ × _ × _
The numbers are from 0 to 9, so there are 10 of them.
There are 26 letters in the English alphabet.
10 × 10 × 26 × 26 × 26 × 10 × 10
Answer: 175,760,000