(1) Subject to subsection (2), a pre-sentence report must be filed with the appellate court—
(a) if the child is being held in custody, within 7 days after the making of the order; or
(b) otherwise, within 21 days after the making of the order.
(2) If the pre-sentence report was ordered under section 357 to enable diagnosis or assessment of the child's relevant impairment or apparent relevant impairment , the pre-sentence report must be filed with the appellate court—
(a) if the child is being held in custody, within 21 days after the making of the order; or
(b) otherwise, within 28 days after the making of the order.
(3) The appellate court may extend a time period specified in subsection (1) or (2).