$$\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2} \cdot \mathrm{XH}_{2} \mathrm{O}$$ and $$\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2} \cdot \mathrm{YH}_{2} \mathrm{O}$$, represent formula of the crystalline forms of nitrate salts. Sum of $$\mathrm{X}$$ and $$\mathrm{Y}$$ is _____________.

On heating, $$\mathrm{LiNO_3}$$ gives how many compounds among the following __________

$$\mathrm{Li_2O,N_2,O_2,LiNO_2,NO_2}$$

BeO reacts with HF in presence of ammonia to give [A] which on thermal decomposition produces [B] and ammonium fluoride. Oxidation state of Be in [A] is ____________.