Prove n O(n²)by choosing some c>0 and n₀ such that n c n² for n n ₀

Which of the following is NOT the correct choice(s) of c and n₀?

Fill in a number between 1-6.

1. c=1, n₀=2
2. c= 1/2, n₀= 1
3. c= 1/2, n₀= 2
4. c= 1/20, n₀= 20
5. c=1, n₀=1
6. no answer found