A 6 in. sch 40 pipeline is designed to carry $\mathrm{SAE} 30$ lube oil at $80^{\circ} \mathrm{F}(\mathrm{SG}=0.87)$ at a maximum velocity of $10 \mathrm{ft} / \mathrm{s}$. You must install an orifice meter in the line to measure the oil flow rate. If the maximum pressure drop to be permitted across the orifice is 40 in. $\mathrm{H}_{2} \mathrm{O}$, what size orifice should be used? If a venturi meter is used instead of an orifice, everything else being the same, how large should the venturi throat be?