Q: mac slow activity monitor wired

You have a Mid 2011 iMac, so you can install 32 GB of RAM. See > http://eshop.macsales.com/shop/memory/iMac/2011/DDR3_21.5_27

It will appear automatically when you use the printer. Just quit it using Activity Monitor. If it doesn't quit, force quit the process

In addition, you also might want to reset your printing system.

as per > OS X Mountain Lion: Reset the printing system

Your iMac has got 4 slots, so you can install 8 GB modules. You can get 2 modules of 8 GB and then, buy other 2 modules of 8 GB. It's easy to install RAM on a iMac > http://support.apple.com/kb/HT1423?viewlocale=en_US#1

Your welcome!

In addition to the OWC Memory installation video,

see > iMac: How to remove or install memory

You can get only two, and later buy other two. You can install 4 slots of 8 GB of memory, but not 32 GB modules

You are welcome

You don't need more memory if all you do is run Firefox.