Air (density 1.2 Kg/m3 and kinematic viscosity 15 centistokes) flows over a flat plate, at zero angle of incidence, at a velocity of 20 m/s. If Reynolds number at transition is taken as 2.5 x 105, maximum distance, from leading edge up to which the boundary layer remains laminar, is
(a) 375 mm (b) 93.75 mm
(c) 187.5mm (d) 250 mm