A ball is shot vertically upward from the surface of another planet. A plot of $y$ versus $t$ for the ball is shown in Fig. $2-36,$ where $y$ is the height of the ball above its starting point and $t=0$ at the instant the ball is shot. The figure's vertical scaling is set by $y_{s}=30.0 \mathrm{~m}$. What are the magnitudes of (a) the free-fall acceleration on the planet and (b) the initial velocity of the ball?