A toy car with charge q moves on a frictionless horizontal plane surface under the influence of a uniform…

$0<t\le 1\mathrm{s}$  velocity increases from $\text{0}$ to $\text{6 m/s}$
$1\mathrm{s}\le t\le 2\mathrm{s}$ : velocity decreases from  $\text{6 m/s}$ to $\text{0 m/s}$
But car continues to move forward and then it reverses its direction at $t=2\mathrm{ s}$ and after $\text{2 s}$ accelerates backward

Distance undefined
$\left|\frac{1}{2}\times 6\times 2\right|+\left|\frac{1}{2}\times \left(-6\right)\times 1\right|$
$=6+3$
$=9\mathrm{ m}$
Displacement = Total area under $\text{v}-t$ graph
$=6-3=3\mathrm{m}$
$\therefore$ Average velocity $=\frac{\mathrm{Displacement}}{\mathrm{Time}}=\frac{3}{3}=1\mathrm{m/s}$
$\therefore$ Average speed $=\frac{\mathrm{Total} \mathrm{distance}}{\mathrm{Time}}=\frac{9}{3}=3\mathrm{m/s}$