In the following unclear reaction,

D $\stackrel{\alpha }{\to }{D}_1\stackrel{{\beta }^{-}}{\to }{D}_2\stackrel{\alpha }{\to }{D}_3\stackrel{\gamma }{\to }{D}_4$  

Mass number of D is 182 and atomic number is 74. Mass number and atomic number of D₄ respectively will be________

Density of nucleus is of the order of

Power factor of series LCR circuit at resonance is

Density of nucleus is of the order of

Two radioactive substances X and Y originally have N₁ and N₂ nuclei respectively. Half life of X is half of the life of Y. After three half lives of Y, number of nuclei of both are equal.

The ratio  $\frac{N_1}{N_2}$  will be equal to: