You must select an orifice meter for measuring the flow rate of an organic liquid ( $\mathrm{SG}=0.8$, $\mu=15 \mathrm{cP}$ ) in a $4 \mathrm{in}$. sch 40 pipe. The maximum flow rate anticipated is $200 \mathrm{gpm}$, and the orifice pressure difference is to be measured with a mercury ( $\mathrm{SG}=13.6)$ manometer having a maximum reading range of $10 \mathrm{in}$. What size should the orifice be?