To determine how many people Rafael can invite if he wants to spend $250 for the party, we can analyze the pricing structure:
- For 1-10 people, the cost is $100.
- For 11-20 people, the cost is $150.
- For 21-30 people, the cost is $200.
- For 31-40 people, the cost is $250.
- For 41-50 people, the cost is $275.
Since Rafael wants to spend exactly $250, he can invite people in the range of 31 to 40 (inclusive).
Thus, the correct response is: 30 < x ≤ 40.