What happens to the mass number and atomic number of an element when it emits gamma-radiation?

Two nuclei have mass numbers A and B respectively. The density ratio of the nuclei is _____________.
Fill in the blank with the correct answer from the options given below.

The half-life of a radioactive sample undergoing α-decay is 1.4×10¹⁷ s. If the number of nuclei in the sample is 2.0×10²¹, the activity of the sample is nearly

In the nuclear emission stated above.
The mass number and atomic number of the product Q respectively, are: