The correct answer is B. 3.2
You can find this answer by using any of the points on the graph and putting them into the given equation. Then you can solve for the constant. For the purpose of this example, we will use (2, 6.4)
Height = Constant * Width ---> Plug in known values.
6.4 = Constant * 2 ----> Divide both sides by 2
3.2 = Constant
This will work with whatever numbers you use from the graph.