Smith Heat and Air Inc. are going out of business. They plan to box up all employee, wage, and payroll tax records and place them in secure storage. How long must they keep the boxes? 

a. 4 years after all returns for the final calendar year have been filed per IRS requirements.

b. 1 year after the final payroll has been filed per EEOC guidelines.

c. 7 years after the final payroll per FLSA guidelines.

d. 3 years after all returns for the final calendar year have been filed per ADEA requirements.