A centrifugal water pump operates at \(1750 \mathrm{rpm}\); the impeller has backward-curved vanes with \(\beta_{2}=60^{\circ}\) and \(b_{2}=1.25 \mathrm{~cm}\). At a flow rate of \(0.025 \mathrm{~m}^{3} / \mathrm{s}\), the radial outlet velocity is \(V_{n_{2}}=3.5 \mathrm{~m} / \mathrm{s}\). Estimate the head this pump could deliver at \(1150 \mathrm{rpm}\).