What is the purpose of the PATH variable?

a$.$ Set the PATH variable and place it in the environment so it causes the shell to search the following directories in order:

$-/$usr$/$local$/$bin

$/$usr$/$bin

$/$bin

$/$usr$/$kerberos$/$bin

The bin directory in your home directory

The working directory

b$.$ If there is an executable file named doit in $/$usr$/$bin and another file with the same name in your $/$bin directory, which one will be executed?

c$.$ If your PATH variable is not set to search the working directory, how can you execute a program located there?

d$.$ Which command can you use to add the directory$/$usr$/$games to the end of the list of directories in PATH?