Answer:
f(x) = 6x - 50
f(-2) = -62, meaning if the company sells -2 shirts, they would make a profit of -62 dollars. This interpretation is not in the context of the problem.
f(7) = -8, meaning if the company sells 7 shirts, they would make a profit of -8 dollars. This interpretation is in the context of the problem.
f(12.5) = 25, meaning if the company sells 12.5 shirts, they would make a profit of 25 dollars. This interpretation is not in the context of the problem.
Based on the observations above, it is clear that an appropriate domain for the function is the set of all non-negative integers.