Except as provided in subsection (b) of this section, a person or governmental unit that wishes to inspect a public record shall submit a written application to the custodian. A person or governmental unit need not submit a written application to the custodian if: the person or governmental unit seeks to inspect a public record listed by an official custodian in accordance with § 4–201(c)(2) of this subtitle; or the custodian waives the requirement for a written application. If the individual to whom the application is submitted is not the custodian of the public record, within 10 working days after receiving the application, the individual shall give the applicant: notice of that fact; and if known: the name of the custodian; and the location or possible location of the public record. When an applicant requests to inspect a public record and a custodian determines that the record does not exist, the custodian shall notify the applicant of this determination: if the custodian has reached this determination on initial review of the application, immediately; or if the custodian has reached this determination after a search for potentially responsive public records, promptly after the search is completed but not more than 30 days after receiving the application.