Find the number of carbonates having $K_{\mathrm{sp}}$value greater than ${\mathrm{Li}}_2{\mathrm{CO}}_3$

${\mathrm{Na}}_2{\mathrm{CO}}_3, {\mathrm{K}}_2{\mathrm{CO}}_3,{ \mathrm{Rb}}_2{\mathrm{CO}}_3 ,{\mathrm{Cs}}_2{\mathrm{CO}}_3$

${\mathrm{Li}}_2{\mathrm{CO}}_3$ has the lowest solubility.

The carbonates having $K_{\mathrm{sp}}$value greater than ${\mathrm{Li}}_2{\mathrm{CO}}_3$ are,

${\mathrm{Na}}_2{\mathrm{CO}}_3, {\mathrm{K}}_2{\mathrm{CO}}_3,{ \mathrm{Rb}}_2{\mathrm{CO}}_3 ,{\mathrm{Cs}}_2{\mathrm{CO}}_3$.

Thus, the correct answer is 4.