For each subset of \(\mathbb{R}\) below, give its supremum, maximum, infimum, and minimum, where possible.
(a) \( \left\{ 1 - \frac{1}{n} : n \in \mathbb{N} \right\} \)
(b) \( \left\{ (-1)^n \left( 1 + \frac{1}{n} \right) : n \in \mathbb{N} \right\} \)
(c) \( \bigcap_{n=1}^{\infty} \left[ \frac{1}{n}, 2 - \frac{1}{n} \right] \)
(d) \( \bigcup_{n=1}^{\infty} \left[ \frac{1}{n}, 2 - \frac{1}{n} \right] \)
