Air at 15°C flows at 10 m/s over a flat plate of length 2 m. Using one-seventh power law of the turbulent flow, what is the ratio of local skin friction coefficient for the turbulent and laminar flow cases? (The kinematic viscosity of air is 1.470 × 10^–5 m²/s.)

(a) 1.25 

(b) 3.72 

(c) 6.31

(d) 8.64 

(e) 12.0