EX #$6$: The graph of the function $g$ consists of a quarter$-$circle and threedine segments, shown at right. Let $f$ be the function defined by:

$f(x)={\displaystyle \underset{-1}{\overset{x}{}}}g(t)dt$

A$.$ Find $f(-5)$

B$.$ Find all the values of $x$ on the open interval $(-5,4)$ where $f$ is decreasing. Justify your answer.

C$.$ Write an equation for the line tangent to the graph of $f$ at $x=-1.$

D$.$ Find the minimum value of $f$ on the closed interval $-5,4.$ Justify your answer.