Answer:
range of f(x) = [-4, -2) ∪ [2, 8)
a+b+c+d = -4
Explanation:
The graph is attached. The range is the vertical extent of the function. It is defined at f(0) = -4 and f(2) = 2.
The limits f(2-) and f(4-) are -2 and 8, respectively, so the graph has open circles there. These are the ends of the two half-open intervals that make up the range of the function.
The portion of the graph in the domain [4, 7) is included in the range [2, 8), so no special treatment is needed for that piece of the function.