A laboratory tests two compounds as starting materials for a condensation polymer. Their structural formulae are shown below.
| Compound | Structural formula |
|---|---|
| R | HO–(CH₂)₄–OH |
| S | HOOC–(CH₂)₂–COOH |
Determine the molecular formula of one repeating unit of the polymer formed from R and S.
Explain how the atoms in R and S form the links in the polymer.