A chemist reacts compounds W and X together to make a polymer.
| Compound | Formula |
|---|---|
| W | HO-CH2-CH2-CH2-OH\text{HO-CH}_2\text{-CH}_2\text{-CH}_2\text{-OH}HO-CH2-CH2-CH2-OH |
| X | HOOC-CH2-CH2-COOH\text{HOOC-CH}_2\text{-CH}_2\text{-COOH}HOOC-CH2-CH2-COOH |
Explain why the polymer produced is a polyester. Give the formula of the other product formed each time a new link is made.