#### Answer

speeding up:
$a = 16~m/s^2$
slowing down:
$a = -5.33~m/s^2$

#### Work Step by Step

The acceleration is equal to the slope of the velocity versus time graph. Therefore,
speeding up:
$a = \frac{\Delta v}{\Delta t} = \frac{0.8~m/s}{0.05~s}$
$a = 16~m/s^2$
slowing down:
$a = \frac{\Delta v}{\Delta t} = \frac{-0.8~m/s}{0.15~s}$
$a = -5.33~m/s^2$