Among the coaches who won the 'NBA coach of the year' award from 1971 - 1975, how many of them were in 'POR' team?
the 'NBA coach of the year' award refers to award = 'NBA coach of the year'; from 1971 - 1975 refers to year between 1971 and 1975; 'POR' team refers to tmID = 'POR'
SELECT COUNT(T1.id) FROM awards_coaches AS T1 INNER JOIN teams AS T2 ON T1.year = T2.year WHERE T1.year BETWEEN 1971 AND 1975 AND T1.award = 'NBA Coach of the Year' AND T2.tmID = 'POR'