Final answer:
Increasing the age of eligibility for Medicare from 65 to 70 would save approximately 4) $400 billion.
Step-by-step explanation:
This reform would decrease the number of beneficiaries and therefore reduce the overall cost of the program. Medicare, a government program that provides health insurance for those 65 and older, is funded differently through various parts.
One of the parts is the Supplementary Medical Insurance, which is financed through beneficiary premiums and general revenues. By increasing the age of eligibility, the number of beneficiaries would decrease, leading to significant savings. Therefore the correct answer is 4) $400 billion.