I have a problem.Installing packages or updating the system is impossible. Neither the Terminal nor the Software Manager are working (Software Manager dosn't start).Terminal shows commands as follows:sudo apt-get updateE: Type 'non-free' is not known on line 3 in source list /etc/apt/sources.listE: The list of sources could not be read.When I try to install a program:sudo apt-get install exfat-utils exfat-fuseReading package lists... DoneBuilding dependency tree       Reading state information... DonePackage exfat-utils is not available, but is referred to by another package.This may mean that the package is missing, has been obsoleted, oris only available from another sourceE: Package 'exfat-utils' has no installation candidateE: Unable to locate package exfat-fusesudo apt-get update && sudo apt-get install autokey-gtkE: Type 'non-free' is not known on line 3 in source list /etc/apt/sources.listE: The list of sources could not be read.sudo apt-get install autokey-gtkReading package lists... DoneBuilding dependency tree       Reading state information... DoneE: Unable to locate package autokey-gtkThe content of my sources list file is as follows:#deb cdrom:[Linux Mint 17.3 _Rosa_ - Release amd64 20151128]/ trusty contrib main non-freedeb http://xnv4.xandros.com/xs2.0/upkg-srv2 etch main contrib      non-freedeb http://xnv4.xandros.com/xs2.0/upkg-srv2 etch main contrib      non-freeThis problem has occurred on my previous Linux Mint (17.0) and reoccurred a few weeks after installing LM 17.3. Thank you very much for your help, I appreciate!
Update and Package Installation impossible: E: Unable to locate package! Linux Mint 17.3
package management;software installation