(a) Classify the following subsets of R as bounded or unbounded. If the set is bounded, write down the supremum and infimum. There is no need to provide proofs for your answers. \text { (i) }\{x:|x-7| \leq 3\} \text {. } \left\{\frac{3}{n^{2}}: n \in \mathbb{N}\right\} \bigcup_{n \text { prime }}\left(-\frac{1}{n^{2}}, \frac{1}{n^{2}}\right) Prove directly from the definition that the sequence \left\{\frac{3 n^{2}}{2 n^{2}+7}\right\} converges toNI CO32 Find the sum of the series \sum_{n=1}^{\infty} \frac{1}{n^{2}+8 n+15}