Answer:
<h2>3 kg</h2>
Explanation:
The mass of the encyclopedia can be found by using the formula

f is the force
a is the acceleration
From the question we have

We have the final answer as
<h2>3 kg</h2>
Hope this helps you
I think it is C , idk why, but I just learn about this and I think it is.... sorry I didn't really help.....