The contour map given below for a function $f$ shows also a path $\mathbf{r}(t)$ traversed counter-clockwise as indicated.
Which of the following properties does the derivative $\frac{d}{dt}f(\mathbf{r}(t))$ have?
I negative at Q,
II positive at R,
III positive at P.
1. I and III only
2. I and II only
3. all of them
4. I only
5. none of them
6. II and III only
7. II only
8. III only