Whenever an agency or person is authorized or required to give any notice under this chapter, unless a different method of giving such notice is otherwise expressly permitted or prescribed, such notice shall be given either by personal delivery thereof to the agency or person to be so notified, or by depositing such notice in the United States mail, postage prepaid, in an envelope addressed to such agency or person at the last-known address of such agency or person. Proof of the giving of notice in either such manner may be made by the affidavit of any officer or assistant or employee of the agency, or by affidavit of any person over eighteen years of age, naming the agency or person to which or to whom such notice was given and specifying the time, place and manner of the giving thereof.
