Please correct the sentences. No sentences has more than one mistake and some sentences are correct. The correction should be three types: (a) word needing to changed and (b) missing word and (c) extra word or no mistake.
1. After finished our work, we went home.
2. Mr Chan bought an used car yesterday.
3. An underground water main burst out in Connaught Road yesterday.
4. Discovery of the gene brought a new hope for liver cancer patients.
5. They are devoted to help children who suffer from AIDS.
6. Paul has been interested in modern dance for a long time.
7. The factory had all its equipment were destroyed in the fire.
8. The missing girl was last seen wearing white T-shirt and jeans.