M: How did you know. <br>A: Because I've been to Mercer's factory, I've been to Milano Window's factory, and we can see some of the production process changes between products of each brand.
M: How do you know that?<br>A: I've been to Mercer's factory, I've been to the window factory in Milan, including some of the production processes between each brand.
M: How do you know that.<br>A: Because I have been to Mercer's factory and Milan window's factory, including the disassembly and replacement of some production processes of products between each brand, we can see.