After of downloading the class-artifacts.tar on Mac, I tried unzip but it doesn't work can somebody help?
if the artifacts are a tar file (not a zip) unzip won't work. therefore you should be able to untar the file with something like: `tar -xvzf ~/Downloads/class-artifacts.tar`.
You can do it using winrar also in wiindows. First Unzip it. Then it will be another file. Rename that file again adding .tar as extension. Then unzip it again using winrar and you will get the files.