Evidence of a statement offered against a party is not made inadmissible by the hearsay rule if:
(a) The statement was made by a person authorized by the party to make a statement or statements for him concerning the subject matter of the statement; and
(b) The evidence is offered either after admission of evidence sufficient to sustain a finding of such authority or, in the court’s discretion as to the order of proof, subject to the admission of such evidence.
(Enacted by Stats. 1965, Ch. 299.)