For the Function $f(x)=\sqrt{x^{2}-8 x+24}-1$ , Find All Values $x$ For Which $f(x)=2$

Multiple Choice

For the function $f(x) =\sqrt{x^{2}-8 x+24}-1$ , find all values $x$ for which $f(x) =2$ .

A) $\{3,-5\}$
B) $\{-3,-5\}$ .
C) $\{3,5\}$
D) $\varnothing$