Write the name of starting materials used for the synthesis of following polymer and identify its monomer unit.

Novolac is prepared from phenol (C₆H₅OH) and formaldehyde (HCHO). It is thus known as phenol-formaldehyde resin commonly as Bakelite. Novolac on heating with formaldehyde (HCHO) undergoes cross linking to form an infusible mass called bakelite.