Answer:
C. 400 J
Step-by-step explanation:
In physics, work is defined as

Where
is the word done,
is the force that move the object and
is the change of the position of the object.
In this case, we have

, remember that the difference refers to the actual subtraction between the final point and the initial point of the object.
Replacing these values, we have

Therefore, the right answer is C. The work done is 400 Joules