The theme that this excerpt shows is that they are going to try to restore what they have taken and fix everything. Think about it like money and buisnessing. You have $20.00 to spend on a lemonade stand, and that is enough for you to be able to make 100 cups of lemonade. 50 people buy 1 cup of lemonade each, so you have 50 cups of lemonade leftover that you save for the next day of buisness. After 3 days, you have sold all 100 of you're cups of lemonade, and now have $100. That means you made a profit of $80, and now you spend another $20.00 and get more money, ultimately leaving you with what you started, and much more! How does this apply to the question? Well, they want to make something that will make more than what it takes, so that it generates its own fuel, and has some to spare! just like how you got more money from the lemonade stand, enough to buy more ingredients for lemonade and some money to spare! Hope this helps!