The flow will become turbulent at

Question

A flat plate of 4m length is kept parallel to  air flowing at 5 m/s at 15⁰C . Assuming the density of air to be 1.2 Kg/m³ and dynamic viscosity to be 1.76 x 10^-5 kg/m-s, and knowing  that the  flow becomes turbulent when Reynolds number eceeds 5 x 10⁵, the flow will become turbulent at         

(a) 1.25 m                    (b) 1.47m                    

(c) 1.52 m                    (d) 1.74 m