$\Lambda$ train accelerates from rest for tine $t_{1}$ at a constant rate $\alpha$ for distance $x$. Then, it decelerates to rest at constant rate $\beta$ in time $t_{2}$ for distance $y$. I'hen,
(a) $\frac{x}{y}-\frac{\beta}{\alpha}$
(b) $\frac{\beta}{\alpha}-\frac{t_{1}}{t_{2}}$
(c) $\frac{x}{y}-\frac{t_{1}}{t_{2}}$
(d) $x-y$