Which of the following may be a use of ${\mathrm{Na}}_2{\mathrm{CO}}_3\cdot 10{\mathrm{H}}_2\mathrm{O}$?

Washing soda(${\mathrm{Na}}_2{\mathrm{CO}}_3\cdot 10{\mathrm{H}}_2\mathrm{O}$ )is used in water softening, laundering and cleaning.

The chemical compound known as washing soda has the formula ${\mathrm{Na}}_2{\mathrm{CO}}_3\cdot 10{\mathrm{H}}_2\mathrm{O}$. Sodium carbonate is present as an inorganic hydrate. Soda ash got its name because it was made from plants that had grown in soil that was high in sodium.