A flat plate is to be coated with a polymer. If the disturbance thickness of the laminar boundary layer that occurs during the coating process at a distance of $0\mathrm{.}5$ m from the plate's front edge is $10$ mm $,$ determine the free$-$stream velocity of this fluid. Take

$u=4\mathrm{.}68({10}^{-6})\frac{m^2}{s}.$

Note: The disturbance thickness is the boundary layer thickness.