Look at the file listing below which was generated by the ls $-$l command:

total $68$

$-$rw$-$r$-----1$ nick staff $126$ Feb $714$:$19$ file$1$

$-$rw$-$rw$-$r$--1$ nick video $77$ Feb $714$:$21$ file$2$

$-$rwxr$-$xr$-$x $1$ nick nick $60438$ Feb $714$:$21$ file$3$

$($a$)$ For each file, who can write information to them? $[6]$

$($b$)$ Which files are executable? $[2]$

$($c$)$ A program is compiled and results in an executable file prog being created in

this directory. When the command prog is issued at the prompt, the following

is printed:

bash: prog: command not found

Why does the program not run, and what could be done to correct this?

$[4]$

$($d$)$ The command ln $-$s file$1$ f$1$ ; ln file$2$ f$2$ is executed and the contents

of this directory are now listed as follows:

lrwxrwxrwx $1$ nick nick $5$ Feb $714$:$40$ f$1->$ file$1$

$-$rw$-$rw$----2$ nick video $77$ Feb $714$:$21$ f$2$

$-$rw$-$r$--$r$--1$ nick nick $126$ Feb $714$:$19$ file$1$

$-$rw$-$rw$----2$ nick video $77$ Feb $714$:$21$ file$2$

$-$rwxr$-$xr$-$x $1$ nick nick $60438$ Feb $714$:$21$ file$3$

$-$rw$-$r$--$r$--1$ nick nick $60641$ Feb $714$:$37$ prog

The user then enters the command rm file$*$ without properly considering the

consequences.

i$.$ If the ls command which produced the above were repeated, which entries

would no longer be present? $[5]$

ii$.$ Are the old contents of file$1$ and file$2$ still accessible through f$1$ and

f$2?$ Explain your answer.