A circular disk of diameter d $=9$in is slowly rotated in a liquid of high viscosity$$at a small distance h$=0\mathrm{.}05$in $$from a fixed surface. The shaft rotates with an angular velocity $250$rpm of the of the disk if the shaft records a torque of $2\mathrm{.}5$ lb$-$ft$.$ Find the viscosity of the liquid $[$lb$-$s$/$ft$2]$