What is the final product (major) 'A' in the given reaction ?

The product formed in the first step of the reaction of


with excess $$\mathrm{Mg/Et_2O}$$ ($$\mathrm{Et=C_2H_5}$$) is

Number of amphoteric compounds among the following is ________.
(A) BeO
(B) BaO
(C) Be(OH)₂
(D) Sr(OH)₂

The stepwise formation of $${\left[ {Cu{{\left( {N{H_3}} \right)}_4}} \right]^{2 + }}$$ is given below:


The value of stability constants K₁, K₂, K₃ and K₄ are 10⁴, 1.58 x 10³, 5 x 10² and 10² respectively.
The overall equilibrium constants for dissociation of $${\left[ {Cu{{\left( {N{H_3}} \right)}_4}} \right]^{2 + }}$$ is x $$ \times $$ 10^-12.
The value of x is ________. (Rounded off to the nearest integer)