How does gypsum contribute to the setting of cement?

The chemical formula of gypsum is _____.

Choose from the following:

A: ${\mathrm{CaSO}}_5.2{\mathrm{H}}_2\mathrm{O}$

B: ${\mathrm{CaSO}}_4.2{\mathrm{H}}_2\mathrm{O}$

True or false. If false, give the correct statement,

Gypsum is largely used in medical industries.