(a) The Board will require the parent's signed statement showing his or her income, any other sources of support, the amount from each source and his or her expenses during the one-year period.

(b) The Board may also ask the parent for signed statements from other people who know the facts about his or her sources of support.

(c) If the statements described in paragraphs (a) and (b) of this section cannot be obtained, the Board will require other convincing evidence that the parent is receiving one-half of his or her support from the employee.