b) Consider two standard approaches towards achieving IP network multicast - unicast emulation and network-layer multicast. Consider a single sender and 128 receivers. Assume the sender is connected to the receivers through a binary tree of routers. Each time a packet (or copy of a packet) is sent over a single link, it incurs a unit of "cost". Analyse the cost of sending a multicast packet in the case of unicast emulation and network-layer multicast for this topology respectively