) Let A and B be subsets of R, A=\bigcup_{n=2}^{\infty}\left[\frac{1}{n}-\frac{1}{5^{n}}, \frac{n-1}{n}+\frac{1}{5^{n}}\right] \quad B=\left\{\frac{3 n^{2}+4 n-6}{n^{2}+n+1}: n \in \mathbb{N}\right\} (a) is it open, closed, or compact in R? (b) find the

interior points, limit points, and isolated points.