In a laminar boundary layer over a flat plate, what would be the ratio of wall shear stress $\tau _{1}$ and $\tau _{2}$ at the two section which lie at distances $X_{1}$ =30 cm and $X_{2}$=90 cm from the leading edge of the plate?
(a) $\tau _{1}$/ $\tau _{2}$=3.0 (b) $\tau _{1}$/ $\tau _{2}$=1/3
(c) $\tau _{1}$/ $\tau _{2}$=(3.0)1/2 (d) $\tau _{1}$/ $\tau _{2}$=(3.0)1/3
