A skydiver is falling straight down, along the negative y direction. $($a$)$ During the initial part $($part a of the figure$)$ of the fall, her speed increases from $15\mathrm{.}0$ m$/$s to $27\mathrm{.}0$ m$/$s in $1\mathrm{.}50$ s$,$ as in part a of the figure. $($b$)$ Later $($part b of the figure$),$ her parachute opens, and her speed decreases from $46\mathrm{.}0$ m$/$s to $29\mathrm{.}0$ m$/$s in $11\mathrm{.}0$ s$,$ as in part b of the drawing. In both instances $($parts a and b of the figure$)$ determine the magnitude and direction $($include sign$)$ of her average acceleration.