Answer
$Amplitude=\frac{5}{3}$
$Period=24$
Work Step by Step
If $y=a~cos(bx)$
$Amplitude=|a|$
$Period=\frac{2\pi}{b}$
$y=-\frac{5}{3}~cos(\frac{\pi x}{12})$
$Amplitude=|-\frac{5}{3}|=\frac{5}{3}$
$Period=\frac{2\pi}{\frac{\pi}{12}}=2\pi\frac{12}{\pi}=\frac{24\pi}{\pi}=24$