(a) The Oir model considers a polymer as a random walk in space, with each individual walk having the same energy. We use the Orr model to consider a polymer in one- dimension where the walk consists of steps in either the positive or negative x-direction, as shown in Figure 3. For a polymer of N steps, each of length b, show that the number of random walks with end-to-end distance Ris S2(N;R)=2 N! NR N R + 2 26 26