Consider the following flow diagram for the extraction of borax from colemanite:
$2CaO \cdot 3B_2O_3 + Na_2CO_3 \xrightarrow{\text{aq. medium}} Z \text{ (Residue/ppt)} + \text{Filtrate}$
$\text{Filtrate} \xrightarrow{\text{Crystallisation & Filtration}} X \text{ (in filtrate)} + Y \text{ (Residue)}$
$X + CO_2 \to Y$
Identify compounds $X$ and $Y$ respectively.

• A
  $Na_2B_4O_7 \cdot 10H_2O, B_2O_3$
• B
  $NaBO_2, Na_2B_4O_7 \cdot 10H_2O$
• C
  $NaBO_2, CaCO_3$
• D
  $Na_2B_4O_7 \cdot 10H_2O, CaCO_3$