Answer:
Option: B is the correct answer.
B) {0 ≤ x ≤ 600}
Explanation:
We are given a profit function in terms of x where x is the number of shirts ordered as follows:

Now, we know that the domain of a function are the possible values of the independent variable for which a function is defined i.e. the possible values of x for which P is defined.
x has to be greater than equal to 0.
i.e. either none of the t-shirts are ordered or some.
and x has to be less than or equal to 600.
Hence, the domain is:
0 ≤ x ≤ 600