The cost function \( C(x) = 30x \) defines the total cost of the field trip based on the number of students \( x \). Since \( x \) represents the number of students, it must be a non-negative integer (0, 1, 2, 3, ...), as you can't have a negative number of students or a fractional/student decimal.
Let's evaluate each option:
- 22: This is a valid input since it's a non-negative integer.
- 15: This is also a valid input since it's a non-negative integer.
- 45: This is a valid input since it's a non-negative integer.
- 14 3/4: This is not a valid input because it is not a whole number (it's a fraction).
- 4.5: This is not a valid input because it is not a whole number (it's a decimal).
Therefore, the possible inputs (domain) for the function \( C(x) \) are:
- 22
- 15
- 45