For a nucleus of mass number A and radius R, the mass density of nucleus can be represented as

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

Assertion (A): The density of the copper $(^ {64}_{29} \text{Cu})$ nucleus is greater than that of the carbon $(^ {12}_{6} \text{C})$ nucleus.

Reason (R): The nucleus of mass number A has a radius proportional to $ A^{1/3} $.

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

In a hydrogen like ion, the energy difference between the $2^{\text {nd }}$ excitation energy state and ground is 108.8 eV . The atomic number of the ion is:

For a hydrogen atom, the ratio of the largest wavelength of Lyman series to that of the Balmer series is