B$1\mathrm{.}1(15$ pts$)$ A falling$-$sphere viscometer was used to determine

the viscosity of a slag used for producing copper. Using a steel

ball of density ${}_b=7\mathrm{.}85{10}^{3}kg{m}^{-3}$ and radius $R=88\mathrm{.}7mm$

as the sphere, falling with terminal velocity $V_t=1\mathrm{.}52m{s}^{-1},$ the

viscosity of the slag was reported as $=441$ Poise $(\{$:$44\mathrm{.}1(N)(s)m^{-2}).$

Taking the density of the slag melt $({}_m)$ to be one$-$half that of the

steel ball $({}_m=\frac{1}{2}{}_b)$ compute the drag coefficient, $C_D,$ and use

the correlation graph below to determine the viscosity of the slag.

Is the reported value given above valid? Explain your answer.