An electric current I $=0\mathrm{.}35$ A is flowing in a long wire. Consider a rectangular area with one side parallel to the wire and at a distance c $=0\mathrm{.}025$ m away from the wire. Let the dimensions of the rectangle be a $=0\mathrm{.}012$ m and b $=0\mathrm{.}074$ m$.$ Express the magnitude of the magnetic field generated by the wire B at a distance r in terms of I and r$.$