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.
- $f(x) = \begin{cases}x^{2}, & x<-1 \\ a x+b, & -1 \leq x \leq 5 \\ x+20, & x>5\end{cases}$

A) $\mathrm{a}=4, \mathrm{~b}=5$
B) $a=-4, b=5$
C) $a=4, b=-5$
D) impossible