OS X :: Close All Open Screens At Once?

I would like to know how I can get one single info screen from the files I have selected. For example I have been working on my music files lately and I often want to get information about the size of the selected music files or music folders. But when I select them I don't get one screen telling me how big the selected files all together are, but a screen will open for every single file or folder. So you need to calculate it by yourself in order to get the total sum. Is there a way to avoid this? Then another thing: I can't find a function for closing all the open screens at once. Is there a way how I could close them all at once, because now I need to close them all separately. Like a couple of days ago I accidentally opened something which contains like 100 folders or more even. When I found it out, I couldn't stop it anymore and all the screens started to open. I had to close all the more than 100 screens one by one.