Under the social contract theory how do leaders gain the right to rule

What is it called when countries build lots of weapons to store and them in case of a war?

In 1914, alabama produced 1.7 million bales of cotton, but three years later produced only 515,000, bales. meanwhile, in georgia, 5.2 million acres of land was dedicated for cotton production in 1914, but by 1923 there were just 2.6 million acres used for growing cotton. all of this was the result of the work of a tiny insect: the boll weevil. alabama and georgia first felt the effects of the boll weevil at different times. what would account for this difference in timing?

Any study/memorization tips? i have exams in a week and it would be great to try suggestions!you ; )