What is the momentum thickness for the boundary layer?

Question

The velocity distribution in laminar boundary layer is given by the relation $\frac{u}{u_{\infty }}$=y/$\delta$  . What is the momentum thickness for the boundary layer?

         (a) $\delta /2$        (b) $\delta /3$     (c) $\delta /4$        (d) $\delta /6$