A ferromagnetic material as shown with a square cross$-$sectional area of $16c{m}^2$ has a relative permeability of $1000.$ The number of turns in the coil is $1000.$ If the outer $($maximum$)$ circumference of the core is $55\mathrm{.}0$ cm $,$ the current required to produce a flux of $6\mathrm{.}4mWb$ is $\_\_$

A$.$

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