\( 2.8 \times 10^{-3} \, \text{mol} \) of \( \mathrm{CO_2} \) is left after removing \( 10^{21} \) molecules from its '\( x \)' \( \text{mg} \) sample. The mass of \( \mathrm{CO_2} \) taken initially is:
[Given: \( N_A = 6.02 \times 10^{23} \, \text{mol}^{-1} \)]