Air flows from the atmosphere into an evacuated tank through a convergent nozzle of \(38-\mathrm{mm}\) tip diameter. If atmospheric pressure and temperature are \(101.3 \mathrm{kPa}\) and \(15^{\circ} \mathrm{C}\), respectively, what vacuum must be maintained in the tank to produce sonic velocity in the jet? What is the flow rate? What is the flow rate when the vacuum is \(254 \mathrm{~mm}\) of mercury?