Analysis of the density of an electrically neutral $NaCl$ crystal containing vacancies yielded the following results:
$(i)$ Density of $NaCl$ crystal with all sites occupied $= 2.178 \times 10^3 \ kg \ m^{-3}$
$(ii)$ Density of $NaCl$ crystal with vacancies $= 2.165 \times 10^3 \ kg \ m^{-3}$
Then the percentage of vacancies in the $NaCl$ crystal is .....

• A
  $5.96 \times 10^{-2} \%$
• B
  $5.96 \times 10^{-1} \%$
• C
  $5.96 \%$
• D
  $8.68 \%$