Problem $9$: Water is flowing at $1\mathrm{.}25cfs$ in a $6-$in diameter water main connecting fire hydrants. Pressures and elevations at two hydrants, which are $1200ft$ apart, are measured and given below Calculate the Hazen$-$William coefficient of the pipe line. Ignore minor losses.

$\backslash$table$[[$Fire Hydrant,Elevations $($ft$),$Pressure $($psi$)],[$A$,255,76],[$B$,246,68]]$

$($A$)107$

$($B$)137$

$($C$)148$

$($D$)160$

In the NCEES Handbook a version of the Hazen$-$Williams equation is provided as pressure. I tried to solve using it but it didn't provide the correct answer. Is the equation wrong or am I using it incorrectly? I keep getting $171.6\mathrm{.}3\mathrm{.}1\mathrm{.}3$ Circular Pipe Head Loss $($as pressure$)$

$P=\frac{4\mathrm{.}52Q^{1\mathrm{.}85}}{C^{1\mathrm{.}85}{D}^{4\mathrm{.}87}}$

where

$P,=$ pressure loss per unit length $of$ pipe $(psi$ per foot $of$ pipe$)$

$Q,=$ flow $(gpm)$

$D-$pipe diameter $(inches)$

$C,=$ Hazen$-$Williams coefficient