An Internet user has subscribed to a 2-Mbps ADSL service. Her neighbor has sub- scribed to a cable Internet service that has a shared bandwidth of 12 MHz. The modu- lation scheme in use is QAM-64. There are n houses on the cable, each with one computer. A fraction f of these computers are online at any one time. Under what conditions will the cable user get better service than the ADSL user?