Answer:
In this letter, you should:
1 - talk about the concept of State (or Power), considering the point of view of each philosopher;
2 - the idea behind the social contract, once again understanding the perspective of Hobbes and Locke;
3 - the State limitations, and the benefits of it, once again putting the ideas of each philosopher in perspective
Now, when it comes to the 18th-century despots, I think the better approach you have in hand is using the Divine Right of the Kings, a theory first stated in the 17th century.
Explanation:
Thomas Hobbes understand the idea that human being needs a strong state, and centralized power to maintain peace. They were living in a natural state, but with constant conflicts. To create a sense of "peace", humans offer their liberty to strong power and creates a state. Because of that, absolute monarchies is the better idea. Hobbes compares the political power of the state to a Leviatan, a mythological monster with several tentacles. And to control a monster such as this, a strong hand was necessary. An absolutist government, according to him, would maintain peace.
On the other hand, Jonh Locke stated that a limited power was a better idea because once you put limits in a power, you can control it. The theory of the limited state is understood as an attempt to maintaining the order and the power on the hands of the people. Even with a king or emperor, it was necessary that people had control of the situation to obtain prosperity.
