Answer:
Is the power produced directly proportional to the wind speed.
No.
A proportional function can be described as y = a * x
So (0, 0) is on the graph, not (3, 0).
0 / 3 = 0
3800/6 = 633.33
7600/9 = 844.44
13600/12 = 1133.33
The quotient y/x should be always the same.