A fixed$-$bed carbon adsorption system consisting of two $6-$foot deep beds containing $6$ x $16$

mesh carbon operates at a superficial gas velocity of $60$ ft$/$min$.$ Specify the horsepower of the

fan motor for the $9,000-$cfm system if the total pressure drop across the system excluding the

pressure drop across the bed is $5$ in$.$ H$2$O