Answer
$\pm0.50\;cm$
Work Step by Step
When,
$P=0$
Therefore,
$\cos(kx-\omega t)=0$
Thus,
$\sin(kx-\omega t)=\pm 1$
$\therefore$ When this minimum transfer occurs, the transverse displacement y becomes
$y=0.50\times (\pm 1)\;cm=\pm0.50\;cm$