The graph of y = f(x) is shown below, with one unit between grid lines. Assume f(x) is defined only on the domain shown. What is the sum of all integers c for which the equation f(x) = c has exactly 6 solutions?
+37146 Only at c = 0 is there 6 solutions
the only place an integer line of 'y' crosses the graph in six places is at y = 0
