Angles — practice question

The diagram depicts triangle $ABC$, which is isosceles, with $AC$ parallel to $BD$. The angle at $C$ is $40^{\circ}$. The points $A$, $B$, $C$, $D$ are labelled. At $B$, the angle between $AB$ and $AC$ is marked $a^{\circ}$, and the angle between $AC$ and $BD$ is marked $b^{\circ}$. The diagram is marked NOT TO SCALE.