A car accelerates from rest at a constant rate \( \alpha \) for some time after which it decelerates at a constant rate \( \beta \) to come rest. If the total time elapsed is \( t \) seconds, the total distance travelled is:
\( \frac{\alpha \beta}{2(\alpha + \beta)} \, t^{2} \)
\( \frac{4 \alpha \beta}{(\alpha + \beta)} \, t^{2} \)
\( \frac{2 \alpha \beta}{(\alpha + \beta)} \, t^{2} \)
\( \frac{\alpha \beta}{4(\alpha + \beta)} \, t^{2} \)