Step 1: Analyze statement (1).
Let \( q \) represent the monthly quota. From statement (1), we know that one salesperson exceeded the quota by 8 cars, and their total commission was $7,500. The commission breakdown is:
\[
\text{Commission for quota} = 250q, \quad \text{Commission for exceeding quota} = 500 \times 8 = 4,000.
\]
Thus, the total commission is:
\[
250q + 4,000 = 7,500 \quad \Rightarrow \quad 250q = 7,500 - 4,000 = 3,500 \quad \Rightarrow \quad q = \frac{3,500}{250} = 14.
\]
So the monthly quota is 14 cars. Therefore, statement (1) alone is sufficient to determine the quota.
Step 2: Analyze statement (2).
Let \( q \) represent the monthly quota. From statement (2), we know that the salesperson achieved half the quota and received $1,750 in commission. The commission for half the quota is:
\[
\text{Commission for quota} = 250 \times \frac{q}{2} = 125q.
\]
Since the total commission is $1,750, we have:
\[
125q = 1,750 \quad \Rightarrow \quad q = \frac{1,750}{125} = 14.
\]
Thus, the monthly quota is 14 cars. Statement (2) alone is also sufficient to determine the quota.
Conclusion:
Both statements together provide sufficient information to determine the quota, and either statement alone is sufficient. Therefore, the correct answer is (C).