A rowland ring of mean radius $15\;cm$ has $3500$ turns of wire wound on a ferro magnetic core of relative permeability 800. What is the magnetic field B in the core for a magnetizing current of $12.A$?

Question

$\begin{array}{1 1} 44.8T \\ 448\;T \\ 4.48\;T \\ 4480\;T \end{array}$