Assignment:
Use the Fundamental Counting Principle to determine the number of 3-letter expressions possible under the following circumstances: The first letter must be a vowel (a, e, i, o, or u); the second letter can be any letter except a vowel; the third letter can be any letter of the alphabet. Remember that there are 26 letters in the alphabet.
Provide complete and step by step solution for the question and show calculations and use formulas.