A 2 in. sch 40 pipe carries $\mathrm{SAE} 10$ lube oil at $100^{\circ} \mathrm{F}(\mathrm{SG}=0.928)$. The flow rate may be as high as $55 \mathrm{gpm}$, and you must select an orifice meter to measure the flow rate.

(a) What size orifice should be used if the pressure difference is measured using a DP cell having a full-scale range of $100 \mathrm{in} . \mathrm{H}_{2} \mathrm{O}$ ?

(b) Using this size orifice, what is the flow rate of oil in gpm when the DP cell reads $50 \mathrm{in}$. $\mathrm{H}_{2} \mathrm{O}$ ?