Air (kinematic viscosity = 
with a free stream velocity of $15\times 10^{-6}$ m2/s flows over a smooth two – dimensional flat plate. If the critical Reynolds number is $5\times 10^{5}$, what is the maximum distance from the leading edge up to which laminar boundary layer exists?
(a) 30 cm (b) 75 cm (c) 150 cm (d) 300 cm