... cardinality of E, i.e. the number of irreducible components of double curves in X;• fn: the number of n-faces of G, i.e. the number of En-points of X, forn 3;• f :=n3fn, the number of ... of G, i.e. the total number of En-points of X, for all n 3;• rn: the number of open n-faces of G, i.e. the number of Rn-points of X,for n 3;• r:=n3rn, the total number of ... if and only if ν =2,i.e.if and only if either n = 3and X consists of a plane and a quadricmeeting along a line, or n = 4and X consists of two quadricsmeeting along a line.(ii) If r = n +1and...