It is necessary to pump water at $70^{circ} mathrm{F}left(P_{mathrm{v}}=0.35 mathrm{psia} ight)$ from a well that is $150

It is necessary to pump water at $70^{\circ} \mathrm{F}\left(P_{\mathrm{v}}=0.35 \mathrm{psia}\right)$ from a well that is $150 \mathrm{ft}$ deep, at a flow rate of $25 \mathrm{gpm}$. You do not have a submersible pump, but you do have a centrifugal pump with the required capacity that cannot be submerged. If a $1 \mathrm{in}$. sch 40 pipe is used, and the NPSH of the pump is $15 \mathrm{ft}$, how close to the surface of the water must the pump be lowered for it to operate properly?