Answer
Amplitude: $4$, period: $2$.
Work Step by Step
If a function has form $y=A\cos(\alpha x)$, then there $|A|$ stands for the amplitude and $T =\frac{2\pi}{\omega}$ stands for the period.
Hence here $|A|=|-4|=4$ and $\omega=\pi$, hence $T=\frac{2\pi}{\omega}=\frac{2\pi}{\pi}=2.$
