Find Numbers $a$ And $b$ , Or $k$ , So That $f$ Is Continuous at Every Point

Multiple Choice

Find numbers $a$ and $b$ , or $k$ , so that $f$ is continuous at every point.
- $f(x) = \begin{cases}4, & x<3 \\ a x+b, & 3 \leq x \leq 5 \\ 2, & x>5\end{cases}$

A) $\mathrm{a}=-1, \mathrm{~b}=-3$
B) $a=-1, b=7$
C) $\mathrm{a}=4, \mathrm{~b}=2$
D) impossible