A long hollow cylindrical conductor $($inner radius $2\mathrm{.}2$mm$,$ outer radius $5\mathrm{.}7$mm$)$ carries a current of $27$A distributed uniformly across its cross section. A long thin wire that is coaxial with the cylinder carries a current of $48$A in the opposite direction. What is the magnitude of the magnetic field a$)1\mathrm{.}0$mm$,$ b$)2\mathrm{.}4$mm$,$ and c$)6\mathrm{.}3$mm from the central axis of the wire and cylinder?