(1) After default, the grantor and the secured creditor may —
(a) exercise any right under this Part; or
(b) exercise any right provided in the security agreement.
(2) The exercise of a right after default does not prevent the exercise of another right after default, except to the extent that the exercise of a right makes the exercise of another right impossible.
(3) Before default, a grantor or debtor may not waive or vary, by agreement, any of its rights under this Part.