Number of molecules in a volume of $$4\,\text{cm}^3$$ of a perfect monoatomic gas at some temperature T and at a pressure of $$2\,\text{cm}$$ of mercury is close to? (Given, mean kinetic energy of a molecule (at T) is $$4 \times 10^{-14}\,\text{erg}$$, $$g = 980\,\text{cm s}^{-2}$$, density of mercury $$= 13.6\,\text{g cm}^{-3}$$)

A

$$4.8 \times 10^{18}$$

B

$$4.0 \times 10^{18}$$

C

$$5.8 \times 10^{16}$$

D

$$5.8 \times 10^{18}$$