Let \(\mu\) be a \(\sigma\)-finite measure on the measurable space \((X, \mathscr{A})\). Show that there exists a finite measure \(P\) on \((X, \mathscr{A})\) such that \(\mathscr{N}_{\mu}=\mathscr{N}_{P}\), i.e. \(\mu\) and \(P\) have the same null sets.