9. (1) Where, under a provision of this Part, a person has a right or obligation to—
(a) do an act in relation to another person in a specified way, or within a specified period; or
(b) give a notice to another person in a specified way, or within a specified period;
the first-mentioned person and the other person may make an agreement for the act to be done or the notice to be given, as the case may be, in another way or within a longer period.
(2) If such an agreement is made, and—
(a) the act is done in accordance with the agreement; or
(b) the notice is given in accordance with the agreement;
the first-mentioned person is taken—
(c) to have performed the act in the way specified in the provision; or
(d) to have given the notice within the time specified in the provision;
as the case may be.