Answer:
vector of zero magnitude
Step-by-step explanation:
The displacement is a vector magnitude, therefore, in addition to being a module, it has direction and sense.
In this case it moved 350 m and then returned the same 350 m, so the total displacement is zero.
If we draw the vector, one has a directional direction to the right and the other direction to the left, therefore when adding the two vectors gives a vector of zero magnitude