Medicare is a federal insurance program that pays for covered health care services of most individuals aged 65 and over and certain disabled persons. In 2013, the program is expected to cover 52 million persons (43 million aged and 9 million disabled) at a total cost of $594 billion. Most individuals (or their spouses) who are 65 and older, and have worked in covered employment and paid Medicare payroll taxes for 40 quarters receive premium-free Medicare Part A (Hospital Insurance). Those entitled to Medicare Part A (regardless of whether they are eligible for premium-free Part A), have the option of enrolling in Part B, which covers such things as physician and outpatient services and medical equipment.