$g$ is a piecewise function composed of line segments and a semicircle.

a$)$ Let $G(x)={\displaystyle \underset{-3}{\overset{x}{}}}g(t)dt.$ Find the following: round to $2$ decimal places as needed

$G(0)=$

$G(3)=$

$G(6)=$

$G(12)=$

$G(15)=$

$G(18)=$

b$)$ On what open intervals is $G(x)$ increasing? Decreasing? Check all that apply

$G(x)$ is increasing on

$(6,15)$

$(-2,0)$

$(0,6)$

$(15,18)$

and decreasing on

$(15,18)$

$(6,15)$

$(-2,0)$

$(0,6)$

c$)$ Find the location of all local extrema of $G(x)$ by determining where $G(x)$ switches from increasing to decreasing and from decreasing to increasing. Use a comma to separate the values of $x$ if there is more than one value.

Local extrema of $G(x)$ occur at $x=$