Hint: Try to construct the queries your adversary algorithm will make to the PRF oracle

$($a$)F_{}^{\text{'}}(x)=F(0||x)||F(0||x),$ where $||$ appends the output of $F(0||x)$ with the output of

$F(0||x)$;$0||x$ is a string where we append $x$ to $0$

$($b$)F_{}^{\text{'}}(x)=F(1||x)||F(x||1).$ Refer to the above for definition of the $||$ operator; $1||x$ is a

string where we append $x$ to $1,$ and $x||1$ is a string where we append $1$ to $x$

$($c$)F_{}^{\text{'}}(x)=F(0||x)||F(0||hat(x)).$ Refer to the above for definition of the $||$ operator. hat$(x)=$

$xo+1^{n-1}$ where $1^{n-1}$ is string of length $n-1$ of all $1\text{'}$s and $o+$ is bitwise XOR operator.