The ionic radii of A^+ and B^- ions are 0.98 × 10^-10 m and 1.81 × 10^-10 m. The coordination number of each ion in AB is

The ionic radii of $\displaystyle \mathrm{A}^{+}$ and $\displaystyle \mathrm{B}^{-}$ ions are $\displaystyle 0.98 \times 10^{-10} \mathrm{~m}$ and $\displaystyle 1.81 \times 10^{-10} \mathrm{~m}$. The coordination number of each ion in AB is