How is the following resin intermediate prepared and which polymer is formed by this monomer unit?

(N/A) The resin intermediate is prepared by the reaction of $Melamine$ with $Formaldehyde$ $(HCHO)$.
This reaction involves the nucleophilic addition of the amino group of $Melamine$ to the carbonyl group of $Formaldehyde$.
The resulting resin intermediate undergoes further polymerization to form the $Melamine-Formaldehyde$ polymer (also known as $Melamine$ resin).
The process is shown below:
$Melamine + HCHO$ $\rightarrow \text{Resin intermediate}$ $\xrightarrow{\text{Polymerization}} \text{Melamine polymer}$