Answer
The direction of the magnetic field at point $b$ is out of the page.
Work Step by Step
The current in the top wire is directed to the left. By the right hand rule, the direction of the magnetic field at point $b$ is out of the page.
The current in the bottom wire is directed to the right. By the right hand rule, the direction of the magnetic field at point $b$ is out of the page.
Therefore, the direction of the net magnetic field at point $b$ is out of the page.
