7—The authority shall, if there are reasonable grounds for doing so, by notice in writing served on the person so entitled, extend (or further extend) the period within which—
(a)under paragraph 2, he may request them to notify him of the terms and conditions proposed for their acquisition of the interest to be acquired;
(b)under paragraph 4, he may request them to strike out or vary the term or condition;
(c)under paragraph 5, he may apply to the sheriff for determination of a matter; or
(d)under paragraph 6, he may serve a notice of acceptance on them;
whether or not the period has expired.