Which of the following statements concerning tax credits is true?

a. For the rehabilitation credit, expenditures to rehabilitate property placed in service before 1936 are eligible for a 20% credit.

b. The work opportunity tax credit is calculated on the amount of wages paid per eligible employee during the first year of employment. The maximum credit is $2,400 per eligible employee.

c. The foreign tax credit is available for business entities, such as corporations, but not for individuals.

d. Unused general business credits are carried back two years and forward 20 years.