a
(a)Both points \( A\) and \(B\) lying on the axis of the magnet and on axial position
\(B \propto \frac{1}{{{d^3}}}\)\(⇒\) \(\frac{{{B_A}}}{{{B_B}}} = {\left( {\frac{{{d_B}}}{{{d_A}}}} \right)^3} = {\left( {\frac{{48}}{{24}}} \right)^3} = \frac{8}{1}\)