A steady viscous flow encountered a solid wall. The surface normal vector of the wall was perpendicular to the flow direction. After the fluid traveled on the wall for a distance x1, the flow started to shift from laminar to turbulent flow, with Re barely reaching 4000 . Fluid has constant density and viscosity of and , respectively. Ignore gravity. Answer the followings ( 20 pts each) 1) Compare boundary layer thickness () and the drag coefficient (Cf) on the surface, right before and after the distance x1 as well as at x2=10x1. 2) What is the critical travel distance (xb) that the boundary layer become thicker than the laminar flow? Give answers in the unit of x1 3) What is the critical travel distance (xd) that drag coefficient becomes less than the laminar flow? Give answers in the unit of x1