The graph of a function $y=f(x)$ is shown. At which point(s) are the following true?
(a) $\frac{d y}{d x}$ and $\frac{d^{2} y}{d x^{2}}$ are both positive.
(b) $\frac{d y}{d x}$ and $\frac{d^{2} y}{d x^{2}}$ are both negative.
(c) $\frac{d y}{d x}$ is negative but $\frac{d^{2} y}{d x^{2}}$ is positive.