Cathode rays were shown to be a stream of "electrons".
Cathode rays (likewise called an electron beam) are streams of electrons saw in vacuum tubes. In the event that a cleared glass tube is outfitted with two anodes and a voltage is connected, the glass inverse the negative terminal is seen to sparkle from electrons radiated from the cathode. Electrons were first found as the constituents of cathode beams. The picture in an exemplary TV is made by centered light emission redirected by electric or magnetic fields in cathode ray tubes (CRTs).
The force pushing back to you would be 5 newtons as Newtons 3rd law says that every action force has an opposite but equal reaction force acting upon it (if i remember correctly )
We Know, P = m*v
Here, m = 30 Kg
v = 5 m/s
Substitute it into the expression,
P = 30*5 Kgm/s
P = 150 Kgm/s
So, your final answer is 150 Kg.m/s
Hope this helps!
B might be the correct answer