All of the following statements concerning Social Security benefits are correct except

 a. The maximum family benefit is determined through a formula based on the worker's PIA. 

b. If a worker applies for retirement or survivors' benefits before his 65th birthday, he must also file a separate application for Medicare. 

c. People who are disabled or have permanent kidney failure can get Medicare at any age. 

d. The Social Security Administration is concerned with beneficiaries' combined income, which, on the 1040 federal tax return, includes adjusted gross income and nontaxable interest income.