Answer:
The final velocity of the thrower is
and the final velocity of the catcher is
.
Explanation:
Given:
The mass of the thrower,
.
The mass of the catcher,
.
The mass of the ball,
.
Initial velocity of the thrower, 
Final velocity of the ball, 
Initial velocity of the catcher, 
Consider that the final velocity of the thrower is
. From the conservation of momentum,

Consider that the final velocity of the catcher is
. From the conservation of momentum,

Thus, the final velocity of thrower is
and that for the catcher is
.
KE = 1/ 2 * 1252 * 144
as KE = 1/2 * m * v ^2
= 90144 J
It's either A or B because it starts off as nuclear energy.
Power is the rate of energy. Mathematically, it is
Power (p) = Energy(E) / Time(t)
Hope this helps!