What is the domain of the relation graphed

I would just like to point out that this is not my personal answer. This same question was asked on a different page. I do not take credit for this

Both personal and government budgeting involve an ongoing process of balancing multiple needs and wants. Both have two types of spending to consider: a personal budget’s fixed expenses correspond to the government’s mandatory spending; the flexible spending in a personal budget corresponds to the government’s discretionary spending. In both types of budgets, overspending can mean taking on debt. An important way that personal budget and government budgets differ is that personal budgets are meant to meet the needs of those in a particular individual or household and rarely involve the income of others. In the case of government budgets, Congress is making decisions about millions of taxpayers’ money and must work to make a budget that takes care of both individual citizens and the national interest.