Operational complexity and right linear grammars

For a regular language L, let Var(L) be the minimal number of nonterminals necessary to generate L by right linear grammars. Moreover, for natural numbers k(1), k(2), ..., k(n) and an n-ary regularity preserving operation f, let g(f)(Var) (k(1), k(2), ..., k(n)) be the set of all numbers k such that there are regular languages L-1, L-2, ..., L-n such that Var(L-i) = k(i) for 1 <= i <= n and Var(f (L-1, L-2, ..., L-n)) = k. We completely determine the sets g(f)(Var) for the operations reversal, Kleene-closures + and *, and union; and we give partial results for product and intersection.