a) In wireless sensor networks (WSN), What is the importance of the MAC layer? why is this MAC layer challenging in networks with shared media? b) Consider the network topology in Figure Q5 shows the hidden terminal problem, where circles indicate the communication and interference range of each node, that is, each node can hear the immediate neighbours to the left and right. Assume that ready-to-send (RTS)/ clear-to-send (CTS) is not being used. i. ii. iii. B [4 Marks] D Figure Q5 Node B currently sends to node A and node C wants to send to node D. Is node C allowed to do so (i.e., can it do so without causing a collision) and will it decide to do so? [3 Marks] Node C sends to node B and node E wants to send to node D. Is E allowed to do so and will it do so? [3 marks] Node A sends to node B and node D sends to node C. Which other nodes are allowed to send at the same time? [3 Marks]