A student makes a short electromagnet by winding $300$ turns of wire around a wooden cylinder of diameter d $=$

$5\mathrm{.}0$ cm$.$ The coil is connected to a battery producing a current

of $4\mathrm{.}0$ A in the wire. $($a$)$ What is the magnitude of the magnetic

dipole moment of this device? $($b$)$ At what axial distance z $$ d

will the magnetic field have the magnitude $5\mathrm{.}0$ T $($approximately

one$-$tenth that of Earth$$s magnetic field$)?$