Lakeside Grill is preparing to open a new outdoor dining patio for the summer. The maximum number of guests allowed on the patio is 108. The owner of the restaurant is planning to fill the patio with square tables that can seat 2 guests and round tables that can seat 6 guests.

If s represents the number of square tables and r represents the number of round tables, which inequality describes this situation?
Which pairs (s,r) represent possible numbers of square and round tables the restaurant owner could put on the patio? Select all that apply.

Inequality: 2s + 6r ≤ 108

Possible pairs (s,r):
1. (0, 18)
2. (4, 14)
3. (8, 10)
4. (12, 6)
5. (16, 2)
6. (20, 0)