#### Answer

a. $\displaystyle \lim_{x\rightarrow 2}F(x)=4,\\$
b. $\displaystyle \lim_{x\rightarrow-1}F(x)=4$

#### Work Step by Step

The graph consists of points (x,f(x)).
When inspecting limits at x=a, approach a on the x axis and
observe what happens to the y-coordinate, f(x), on the graph.
A limit exists only if both one-sided limits exist, and are equal,
-----------
( F is not defined for x=2)
a.
As $x$ approaches 2 from either the left or right,
$F(x)$ gets closer to 4.
Both one-sided limits exist, and are equal,
$\displaystyle \lim_{x\rightarrow 2}F(x)=4$
b.
As $x$ gets closer to $-1$ from left or right,
$F(x)$ gets closer to 4.
Both one-sided limits exist, and are equal,
$\displaystyle \lim_{x\rightarrow-1}F(x)=4$