Starting from rest a particle is first accelerated for time `t_1` with constant acceleration `a_1` and then stops in time `t_2` with constant retardation `a_2.` Let `v_1` be the average velocity in this case and `s_1` the total displacement. In the second case it is accelerating for the same time `t_1` with constant acceleration `2a_1` and come to rest with constant retardation `a_2` in time `t_3.` If `v_2` is the average velocity in this case and `s_2` the total displacement, then
A. `v_2=2v_1`
B. `2v_1ltv_2lt4v_1`
C. `s_2=2s_1`
D. `2s_1lts_2lt4s_1`