Suppose there is a 2 Mbps link shared by multiple users. Each user requires 200kbps when transmitting, but each user transmits only 15 percent of the time. a. How many users can be supported when circuit switching is used? (5 points) b. Suppose packet switching is used, find the probability that a given user is transmitting. (5 points) c. Assume packet switching is used. Suppose there are 100 users. Find the probability that at any given time, exactly n users are transmitting simultaneously. (Hint: Use the binomial distribution.) (10 points) d. Find the probability that there is k or more users transmitting simultaneously (just list the formula with the parameter k ( k can be any integer between 1 and 100)). (10 points)