Answer
Domain = $\mathbb{R}$
Range = $\{y\ |\ y \leq 4\}$, or $(-\infty,4]$
Work Step by Step
If the function is described by a graph, then the domain is the set of all first coordinates of the points on the graph. The range is the set of all second coordinates.
The first coordinate of a point of the graph can be any real number.
Domain = $\mathbb{R}$
The second coordinates are real numbers, $4$ or under $4.$
Range = $\{y\ |\ y \leq 4\}$, or $(-\infty,4]$
