The Coastal Engineering Research Center, in making its report on any cooperative investigation and studies under the provisions of section 426 of this title, relating to shore protection work shall, in addition to any other matters upon which it may be required to report, state its opinion as to (a) the advisability of adopting the project; (b) what public interest, if any, is involved in the proposed improvement; and (c) what share of the expense, if any, should be borne by the United States.