Answer:
Part a)

Part b)

Explanation:
As per momentum conservation we know that there is no external force on this system so initial and final momentum must be same
So we will have




Part b)
By equation of kinetic energy we have




the answer is the forth one treatment of cancer
The answer would be "the vector sum of forces acting on a particle or body."
Hope that helped ^^
1. Frequency 2. measure from trough to trough