Read through it carefully,
1400J of "heat" was added to the system
only 600J of thermal energy was added to the system, or only 600J of the "heat" was used to change the temperature
so if only 600 of 1400J was used to affect the temperature, that means the remaining heat energy must have been converted to work
1400J-600J =
<h2>
18.6467 N</h2>
Explanation:
The Work done by any force is defined as the force applied times the displacement of point of application of force in the direction of force.
This is better represented as a scalar product of Force vector and displacement vector.

Here, the angle between force and displacement is
.



∴ Magnitude of force = 
Answer:
If I'm not working I think the answer is C.