3. In real analysis, or functional analysis, please briefly show your work explicitly and clearly.
3. Let A, B be non-empty compact subsets of (X, d). The Hausdorff distance is
dH(A, B) := max{sup inf d(a, b), sup inf d(a, b)} a∈A b∈B b∈B a∈A
a) Show that dH is a metric b) Let A = [0, 1], B = [3, 5]. Find dH(A, B) in R c) Find dH(A, B) for the same A, B in R with the post office metric d(x, y) = |x| + |y| for x, y, d(x, x) = 0.