In the figure shown the system is at rest initially. Two persons ‘A’ and ‘B’  of masses 40 kg each move with constant speeds  $v_1$  and $v_2$  respectively towards each other on a plank lying on a smooth horizontal surface as shown in  figure. The plank travels a distance of 20 m towards right direction in 5 sec (Here $v_1$  and $v_2$  are  magnitude of velocities with respect  to the plank)  . Then the possible condition (s) can be