Remove kitchen sink drain pipes

kitchen-sinkpipe

I am trying to remove the kitchen sink to replace it. Its drain pipes are showed in the following photo:

Anyone know how to remove these pipes from the sink? It doesn't look like I can turn the part that connects the pipes and the sink.

Best Answer

I asked the company that sold the sink, and they said that the pipe is attached to bottom of the sink with a screw. So the pipe could be removed as in this photo: enter image description here