Given a one-way function h(vi) => hi mapping visitors to unique anonymous tokens, for a set of visitors, v0, v1, ..., vn ∈ V, over a time period T, where t0, t1, ..., tm ∈ T are discreet units. Determine how many unique hi are in a subset of T: d ⊂ T, assuming you have a mapping l(hi) => tj of hi to the last tj it was seen at.
Given the above with mapping ∀ ti ∈ T to ui, calculate the new unique count for a period of k・d.