Binding number, minimum degree and (g,f)-factors of graphs

Let a and b be integers with 2<= a< b, and let G be a graph of order n with n>= (a+b-1)^2/(a+1) and the minimum degree \delta(G)<= 1+(((b-2)n)/(a+b-1)).Let g and f be nonnegative integer-valued functions defined on V(G) such that a<= g(x)<f(x)<= b for each x in V(G).We prove that if the binding number bind(G)>=1+((b-2)/(a+1)), then G has a (g,f)-factor