$$\(A, B, C\)$$ and $$\(D\)$$ lie on the circle, centre $$\(O\)$$. $$\(T A\)$$ is a tangent to the circle at $$\(A\)$$. Angle $$\(A B C=131^{\circ}\)$$ and angle $$\(A D B=20^{\circ}\)$$. Find angle $$\(O A B\)$$. Angle $$\(O A B=..................\)$$

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