1. The problem statement, all variables and given/known data For each subset of ℝ, give its supremum and maximum, if they exist. Otherwise, write none. 2. Relevant equations d) (0,4) 3. The attempt at a solution For part d, if the problem were [0,4], both the supremum and maximum would be 4, since the interval includes the end points, but I'm not sure about when it doesn't. It seems to me that the supremum would still be 4, as that qualifies as a least upper bound because 4 is in the neighborhood of the set, but is the maximum also 4? I don't think it would be since the interval does not include end points, but I'm confused! Thanks!