MACMILLAN PLAN: Both the Greek government of Constantine Karamanlis and Ethnarch of Cyprus Archbishop Makarios have rejected as completely unacceptable the British plan for Cyprus. In its response, the Greek government describes the plan as impossible to implement and likely to complicate the Cyprus issue. Their joint reply is expected to be released today. At the same time, Archbishop Makarios, in a reply to a letter from Cyprus Governor Sir Hugh Foot, emphasized that the plan imposes a triple sovereignty on the island and that that was in contravention of the Cypriot people’s fundamental right to self-determination. He said that a truly democratic constitution called for bilateral talks between the British government and the Cypriot people, which Makarios said he has always been willing to enter into. MARIA CALLAS: The leading Greek soprano Maria Callas has notched up another triumph in her career with her appearance the night before last on a variety program on British television. When she finished singing her aria from «Tosca,» the usually reserved television concert-viewing audience burst into an extended enthusiastic applause in the studio.