How many sentences are written in Present Perfect? Give the answer in number.

The lesson hasn't started yet.
The teacher has already written on the board.
I have been painting my bedroom for the last few days.
I have been thinking of having a party when I finish my exams.
I think I have heard the song before.
Bob has just invited Emma to dinner.
I have been working with my best friend for six years.
I have been writing an e-mail for over an hour.
I have been reading an interview with a famous actor.