Table:
text: Portugal International
Previous winners
Previous winners
Year_ Men_s_singles Women_s_singles Men_s_doubles Women_s_doubles Mixed_doubles
1971 Anton Sauter Fina Salazar Anton Sauter Erich Linnemann no competition Alfredo Salazar Fina Salazar
1972 Philip Smith Nora Gardner Eddy Sutton Bill Kidd Nora Gardner Barbara Giles Bill Kidd Barbara Giles
1973 Ray Stevens Margaret Beck Ray Stevens Elliot Stuart Nora Gardner Barbara Giles Ray Stevens Barbara Giles
1974 Elo Hansen Barbara Giles David Hunt Bill Kidd Margo Winter Barbara Giles David Hunt Margo Winter
1975 no competition no competition no competition no competition no competition
1976 Michael Wilks Jane Webster Michael Wilks Peter Bullivant Jane Webster Kathleen Redhead Peter Bullivant Kathleen Redhead
1977 Tariq Farooq Karen Bridge Ola Eriksson Christian Lundberg Karen Bridge Anne Statt Tim Stokes Karen Bridge

Question: What is the average year for Portugal International with Alfredo Salazar Fina Salazar in mixed doubles?