5. Problem P8 - a slightly-modified version (10 points). Suppose users share a 3 Mbps link. Also suppose each user requires 150 kbps when transmitting, but each user transmits only 10% of the time. (see the discussion of packet switching versus circuit switching in Section 1.3). a. When circuit switching is used, how many users can be supported? b. For the remainder of this problem, suppose packet switching is used. Find the probability that in a group of 120 such users, exactly one user is transmitting. (Hint: Use the binomial distribution.) c. Suppose again that there are 120 users. Find the probability that at any given time, exactly 21 users are transmitting simultaneously