Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : In a particular point defect, an ionic solid is electrically neutral, even if few of its cations are missing from its unit cells.

Reason (R) : In an ionic solid, Frankel defect arises due to dislocation of cation from its lattice site to interstitial site, maintaining overall electrical neutrality.

In the light of the above statements, choose the most appropriate answer from the options given below :

Choose the correct statement:

Copper crystallises in fcc unit cell with cell edge length of 3.608 $$\times$$ 10^$$-$$8 cm. The density of copper is 8.92 g cm^$$-$$3. Calculate the atomic mass of copper.