Evaluate the expression. If the answer is not an integer, round to four decimal places.
$(21-13) !$

Select the correct answer below and fill in the answer box to complete your choice.
A. The value is an integer. $(21-13) !=$
B. The value is not an integer. $(21-13) ! \approx \quad$ (Round to four decimal places as needed.)

Step 1 ：The question is asking for the factorial of the result of the expression \((21-13)\). The factorial of a number is the product of all positive integers less than or equal to that number.

Step 2 ：First, we need to calculate the result of the expression \((21-13)\).

Step 3 ：Then, we will calculate the factorial of the result.

Step 4 ：The factorial of a number is always an integer, so we can already eliminate option B.

Step 5 ：Let's calculate this: the result of the expression \((21-13)\) is 8.

Step 6 ：The factorial of 8 is 40320.

Step 7 ：Final Answer: The value is an integer. \((21-13) ! = \boxed{40320}\)