Question $3$: Air flows through a packed bed of cylindrical particles $($length of $7mm$ and a diameter of $3mm).$ The bed diameter is $5\mathrm{.}0m$ and its height is $3\mathrm{.}0m.$ Air flows at a velocity of $3\frac{m}{s}$ at $300K$ and $1$atm. Assuming the viscosity of the air is $0\mathrm{.}0002$ Pa$.$s$,$ calculate:

a$-Re.$

b$-$ Pressure drop across the packed bed.