Electrostatics

Two charges of \(-4 \mu \mathrm{C}\) and \(+4 \mu \mathrm{C}\) are placed at the points \(\mathrm{A}(1,0,4) \mathrm{m}\) and \(\mathrm{B}(2,-1,5) \mathrm{m}\) located in an electric field \(\overrightarrow{\mathrm{E}}=0.20 \hat{i} \mathrm{~V} / \mathrm{cm}\). The magnitude of the torque acting on the dipole is \(8 \sqrt{\alpha} \times 10^{-5} \mathrm{Nm}\), where \(\alpha=\) _________.