Answer:
Part a)

Part b)
Ball thrown downwards =
Ball thrown upwards =
Part c)

Explanation:
Part a)
Since both the balls are projected with same speed in opposite directions
So here the time difference is the time for which the ball projected upward will move up and come back at the same point of projection
Afterwards the motion will be same as the first ball which is projected downwards
so here the time difference is given as



Part b)
Since the displacement in y direction for two balls is same as well as the the initial speed is also same so final speed is also same for both the balls
so it is given as




Part c)
Relative speed of two balls is given as


now the distance between two balls in 0.8 s is given as



Answer
Explanation:
The question was incomplete as the events are not given in the question. However the answer to your question is given as follows. The correct order of the events from youngest (top) to oldest (bottom) is given as follows.
Moon formation
↑
Earth formation
↑
Nuclear fusion in protosun
↑
BigBang