AMC 12 2007b Problem 3

The point $O$ is the center of the circle circumscribed about triangle $ABC$, with $\angle BOC = 120^{\circ}$ and $\angle AOB = 140^{\circ}$, as shown. What is the degree measure of $\angle ABC$?

$\mathrm {(A)} 35 \mathrm {(B)} 40 \mathrm {(C)} 45 \mathrm {(D)} 50 \mathrm {(E)} 60$