Rafael is trying to book a graduation party. The party pavilion charges $100 for the first 10 people, $150 for 10 more than 10 and up to 20 people, $200 for more than 20 people and up to 30 people, $250 for more than 30 and up to 40 people, and $275 for more than 40 and up to 50 people. If Refael wants to spend $250 for this party, how many people can he invite?

To determine the number of people that Rafael can invite for his graduation party, we need to find the range of values for x that satisfy the given budget of $250.

From the information provided:
- For the first 10 people, the cost is $100.
- For the next 10 people (11th to 20th person), the cost is $150.
- For the next 10 people (21st to 30th person), the cost is $200.

To spend exactly $250, Rafael can invite 10 people for $100, 10 people for $150, and 10 people for $200.

Therefore, the number of people Rafael can invite is 10 + 10 + 10 = 30.

So, the correct answer is:

C. 20 < x ≤ 30