Answer:
The ball experiences the greater momentum change
Explanation:
The momentum change of each object is given by:

where
m is the mass of the object
v is the final velocity
u is the initial velocity
Both objects have same mass m and same initial velocity u. So we have:
- For the ball, the final velocity is

Since it bounces back (so, opposite direction --> negative sign) with same speed (so, the magnitude of the final velocity is still u). So the change in momentum is

- For the clay, the final velocity is

since it sticks to the wall. So, the change in momentum is

So we see that the greater momentum change (in magnitude) is experienced by the ball.
They are positive and remain inside the nucleus.
As v becomes zero at the highest point, i prefer considering different travelling directions so it will become less complicated.
dont forget to add the total time up .
also to master the skills, write down the "uvsat" may help (thats the way i found it easier to handle problems)
I am so sure it's 600,000 x 500 so you get 300,000,000