In a closed system, energy in form of heat (work) can be exchanged but not matter.
The answer to your question is C.
Hope it helped!
If you were given distance & period of time, you would be able to calculate the speed.
Hope this helps!
300N/25 kg= divide them for the answer
B. kinetic energy increases and potential energy decreases
The specific answer for that will be 71.38 kg