$\begin {array} {1 1} (a)\;\large\frac{2BA^2}{\mu_0}\sqrt{\large\frac{2}{\pi}} & \quad (b)\;\large\frac{2BA}{\mu_0}\sqrt{\large\frac{A}{\pi}} \\ (c)\;\large\frac{4BA}{\mu_0}\sqrt{\large\frac{A}{\pi}} & \quad (d)\;\large\frac{BA}{\mu_0}\sqrt{\large\frac{A}{\pi}} \end {array}$