At what position across the pond is the air no longer

Question

A well-mixed open pond contains wastewater that is contaminated with a dilute concentration of dissolved methylene chloride.a

The pool is rectangular with dimensions of 500 m by 100 m. Air 27°C at and 1.0 atm blows parallel to the surface of the pond as shown in the figure with a velocity of 7.5 m/s. At 20°C and 1.0 atm, the diffusion coefficient of methylene chloride in air D_AB  0:085 cm²/s and the kinematic viscosity of the air n_B = 0:15 cm²/s.

(a) At what position across the pond is the air no longer laminar?

(b) Determine the mean gas-film mass-transfer coefficient associated with the transfer of methylene chloride.

(c) What is the Schmidt number for methylene cholride in the liquid phase if at 20°C the diffusion coefficient of methylene chloride in water is 1:07 × 10^-5 cm²/s and the kinematic viscosity of water is 0.010 cm² /s?