Hello there!
Essentially, a control variable is what is kept the same throughout the experiment, and it is not of primary concern in the experimental outcome. Any change in a control variable in an experiment would invalidate the correlation of dependent variables (DV) to the independent variable (IV), thus skewing the results.
We will have the following:

So, the heat to add is 3611.52 Joules.
Answer:
A) Diagonals of a parallelogram bisect each other