Parallel Lines and Angle Calculation

12-

$$d_1 // d_2$$

$$\alpha = ?$$

(The figure shows two parallel lines $d_1$ and $d_2$. There are angles formed by segments. At the top line $d_1$, an angle is bisected (marked with double ticks). At the bottom line $d_2$, another angle is bisected (marked with dots). An intermediate angle is $40^\circ$ and the target angle is $\alpha$.)

This question includes visual content: The image shows two horizontal parallel lines labeled d1 and d2. Between these lines, there are two sets of broken lines forming zigzag patterns. The leftmost vertex of the first pattern is labeled 40 degrees. There are two angle bisector markings on the upper line d1 and two different angle bisector markings (dots) on the lower line d2. A second vertex pointed towards the right is labeled with the Greek letter alpha. A text on the right states d1 // d2 and asks for alpha = ?.