3a Why is the current structure of benefits and funding for U.S. Social Security expected to be unsustainable without a change in the Social Security law? Give a complete set of reasons as you can.

3b Suppose that the only change in the law is a single fixed percentage change in the benefits paid. Every recipient would receive a fixed percentage of the benefit they would receive under current law. Estimate that percentage under the assumption that it will be as close to 100% as possible. Explain how you get your estimate, explaining the main factors that the percentage depends on.