The function $\"\"$ , where $\"\"$ is the number of tickets sold.

Domain of the function is all possible $\"\"$ values.

Domain of the function is all real numbers.

Since $\"\"$ represents number of tickets, the relevant domain of $\"\"$ is all whole numbers from $\"\"$ to the capacity of the stadium.

The domain of the function $\"\"$ is set of whole numbers from $\"\"$ to the capacity of the stadium.