Given that interionic distance in ${\mathrm{Na}}^{+}{\mathrm{F}}^{-}$ crystal is $2.31\stackrel{°}{\mathrm{A}}$ and $r_{\mathrm{F}}=1.36\stackrel{°}{\mathrm{A}}$, which of the following predictions will be right? 

$\frac{r_{{\mathrm{Na}}^{+}}}{r_{{\mathrm{F}}^{-}}}=0.7$

Effective nuclear charge for ${\mathrm{Na}}^{+}$ and ${\mathrm{F}}^{-}$ are equal

${\mathrm{Na}}^{+}{\mathrm{F}}^{-}$ will have rock salt type crystal structure

Coordination number of ${\mathrm{Na}}^{+}=$ coordination number  of ${\mathrm{F}}^{-}=6$