Which of the following compound is formed in borax bead test?

Borax bead contains sodium metaborate and boric anhydride.When heated, borax loses its crystallisation water and expands to form a fluffy mass. As it continues to heat up, it melts into a clear liquid that eventually turns into a transparent, glossy bead made of sodium metaborate and boric unhydride.

${\mathrm{Na}}_2{\mathrm{B}}_4{\mathrm{O}}_7\cdot 10{\mathrm{H}}_2\mathrm{O}\stackrel{\mathrm{\Delta }}{⟶}{\mathrm{Na}}_2{\mathrm{B}}_4{\mathrm{O}}_7\stackrel{\mathrm{\Delta }}{⟶}\underset{\text{ SodiumMetaborate }}{2{\mathrm{NaBO}}_2}+{\mathrm{B}}_2{\mathrm{O}}_3$

Thus, Metaborate is formed.