Set-up: Rubber band modelled as an Ideal chain (polymer) with Nr (links) monomers pointing right, and Nl monomers pointing left each of length l. Find expressions for the length of the band, its statistical weight (iI think that means the multiplicity?) and its entropy, in terms of Nr and Nl. The length L is just, L = (Nr + Nl)l Statistical Weight Ω(S(R)) Entropy is given by S(R) = k.ln (Ω(S(R))) where R is a vector representing the net displacement of the ends. I'm not sure how to get the statistical weight. I know the general formula is Ω(N, a) = (a + N -1) / a!(N-1)!, is a = l in my case?