Find the number of maximal ideal of $R$?

Question

If $R$ is a commutative ring with unity and $I$ is an ideal of $R$ such that any element in $R\setminus I$ has inverse in $R$. Then what will be the number of maximal ideals of $R$?

I think it will be $2$, is it correct?

Answer 1

Hint 1: what can you say about $R/I$?

Hint 2: can an ideal different from $I$ be maximal?