Atoms of an element 'A' occupy $\large\frac{2}{3}$ tetrahedral voids in the hexagonal closed packed ( hcp) unit cell lattice formed by the element 'B' . The formula of the compound formed by 'A' and 'B' is

Question

$\begin {array} {1 1} (1)\;A_2B & \quad (2)\;AB_2 \\ (3)\;A_4B_3 & \quad (4)\;A_2B_3 \end {array}$