Problem $9$: A long flat plate is dragged inside a water pool along its length with a velocity of $40c\frac{m}{s}.$ Derive an expression for ratio of boundary layer thickness at the edge to boundary layer thickness at critical Reynolds number location, if the boundary layer at the edge is a turbuient BL$.$

The length of the plate is selected in such a way that the thickness of turbulent boundary layer at the edge is four times the thickness of critical boundary layer. Estimate the total drag on a $3$ m wide plate.