Two circular arcs have radii a $=13\mathrm{.}5$cm and b $=10\mathrm{.}7$ cm and, subtend angle $74\mathrm{.}0,$ carry current i $=411$ mA$,$ and share the same center of curvature P$.$ a$.)$ The magnitude of the net magnetic field at P is $\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_$ b$.)$ The direction of the net magnetic field at P is: $\_\_\_\_$