Given integers a and b, let Na, b denote the number of positive integers k < 100 such that k ≡ a (mod 9) and k ≡ b (mod 11). Then which of the following statements is correct?
1
Na, b = 1 for all integers a and b.
2
There exist integers a and b satisfying Na, b > 1.
3
There exist integers a and b satisfying Na, b = 0.
4
There exist integers a and b satisfying Na, b = 0 and there exist integers c and d satisfying Nc, d >1.