A print shop runs a two-station binding line, in which the first station punches holes in the pages and the second station installs the binders. On average, the punch machine can process 15,000 pages per hour, while the binder can process 10,000 pages per hour. The shop receives work that requires both punching and binding at a rate of 8,000 pages per hour. It also receives work requiring only punching at a rate of 5,000 pages per hour. Which station is the bottleneck of this line and why? (Be sure to show numeric proof in your answer.)