D.
Since the net force is pointing east, the resulting acceleration is also pointing east.
E.
The work can be calculated with the formula below:
[tex]W=F\cdot d[/tex]Since Gabrielle's force is to the east (same direction of the acceleration), so let's use a positive force:
[tex]W=40\cdot4=160\text{ J}[/tex]This work is positive.
F.
Pierre pushes the box in the opposite direction the box is moving, so his force is negative:
[tex]W=-32\cdot4=-128\text{ J}[/tex]G.
The friction force is acting on the opposite direction of the movement, so it is negative:
[tex]W=-3\cdot4=-12\text{ J}[/tex]H.
adding all works, we have:
[tex]160-128-12=20\text{ J}[/tex]I.
To find the net work in horizontal, let's use the net force in horizontal:
[tex]\begin{gathered} F_{net}=40-32-3=5\text{ N}\\ \\ W_{net}=5\cdot4=20\text{ J} \end{gathered}[/tex]J.
To find the net work in vertical, let's use the net force in vertical:
[tex]\begin{gathered} F_{net}=F_{weight}-F_{normal}=0\text{ N}\\ \\ W_{net}=0\cdot4=0\text{ J} \end{gathered}[/tex]