a$.$ Why is a turbulent viscosity $($and the turbulent diffusivity$)$ of a fluid in a turbulent boundary layer $($i$.$e$.,$ near a wall$)$ lower near the wall than far from the wall

b$.$ Explain mechanistically why the equillibration time of heating a wall is propoertional to the square of the thickness of the wall

C$.$ Why is unimolecular diffusion faster than equimolar counter diffusion, all else being the same