Finding the interior and the closure of a set

Question

Question:

Finding the interior and the closure of a set

Easy: Consider the set A = {x∈ℜ² : x1 = 0 or x2 = 0}. Compute,for the euclidean metric,the interior and the closure of A in ℜ². If you consider A as a subspace,is it complete?

Hard: Consider the st A = {(x^m)∈l^∞ : one and only one component is different from 0}. Compute,for the metric d_∞,the interior and the closure of A in l^∞, If you consider A as a subspace,is it complete?