which of the following statements is true as it applies to a calendar-year taxpayer?

a. a qualified plan must be executed by April 15 and contributions to the plan must be made by the extended due date of the income tax return

b. a qualified plan must be executed by December 31 and contributions to the plan must be made by April 15

c. a qualified plan must be executed by December 31 and contributions to the plan must be made by the extended due date of the income tax return

d. a qualified plan must be executed by the extended due date of the income tax return and contributions to the plan must be made by the extended due date of the income tax return