A current-carrying wire is configured as shown. Find the magnetic field at the center O. Assume into the page is positive.

To find the magnetic field at the center O, we need to consider the contribution from each segment of the current-carrying wire. The total magnetic field will be the vector sum of the fields due to each segment. We will use the right-hand rule to determine the direction of the magnetic field. Let's assume into the page is positive and out of the page is negative.

The configuration consists of:

1. A semi-infinite straight wire A'A.
2. A quarter-circle arc AB.
3. A semi-infinite straight wire B'B.
4. A semi-infinite straight wire C'C.
5. A quarter-circle arc CD.
6. A semi-infinite straight wire