The graph of the invertible function f is shown on the grid below.
←+++
-9-8-7-6-5-4-3-2
9+
67686
7+
5+
4+
3+
2+
1-
43
ଟା
Y
-2-
-3-
-4-
-5+
67
What is the value of f-¹(6)?
-6-
-7+
600
-8-
234
21
9
y = f(x)
+H
789 my