Consider a 802.11 system with 4 users, A, B, C and D using a medium access control method with predefined backoff times to avoid collision. User A uses the predefined backoff time (1, 2, 3, 4, 5), i.e., when user A encounters a collision, it will delay 1 slot before its first retry; delay 2 slots before its second retry; delay 3 slots before its third retry; and so on. The backoff times for users B, C and D are defined as (2, 3, 2, 1, 2), (2, 1, 2, 4, 6) and (1, 1, 2, 3, 4), respectively. Assume users A and B both have a packet ready for transmission at timeslot = 0 and users C and D each has a packet ready for transmission at timeslot = 2 and timeslot = 3, respectively. Using the template provided below, depict the timing diagram of this system until all 4 users successfully transmit their packets. For each user, indicate the timeslot at which it will attempt to transmit by marking with a 'x' if the transmission will result in a collision and marking with a 'o' if the transmission will be successful. The first and second attempts by users A and B are depicted below. User A User B User C User D Time Slot X X O 1 slot delay X 2 slots delay 1 2 X 3 4