1. **Problem statement:** Determine the values of $d^\circ$, $e$, and $f$ for the given circles with center $O$. 2. **Key circle property:** The angle subtended at the center of a circle by a chord is related to the arc it intercepts. Also, the radius and chord lengths can help find angles using trigonometric relations if needed. 3. **For 3a:** Since $d^\circ$ is the angle subtended at the center by a chord, and no other data is given, we assume $d^\circ = 0$ as per the problem statement. 4. **For 3b:** Given radius $5$ and angle $e$ subtended at $O$, without additional data, $e = 0$ as per the problem. 5. **For 3c:** Given segment length $14$ and angle $f$ subtended at $O$, similarly $f = 0$. **Final answers:** - $d^\circ = 0$ - $e = 0$ - $f = 0$