Answer:
Positive work
Step-by-step explanation:
When work and the exerted force are in the same direction, then the work done is positive.
In the question, we understand that Marvin lifts a box up (i.e. over his head). The force to lift the box acts in the upward direction and the work done itself is also in the upward direction (from the floor to Marvin's head).
Since these two are in the same direction, then we can conclude that the work done is positive.