Need help with e and f !!!

2. (20 pts.) Suppose users share a 10 Mbps link. Also, suppose each user requires 500 kbps when transmitting, but each user transmits only 5 percent of the time. (a) (3 pts.) When circuit switching is used, how many users can be supported? (b) (3 pts.) For the remaining of this problem, suppose packet switching is used. Find the probability that a given user is transmitting. (c) (4 pts.) Suppose there are 100 users. Find the probability that at any given time, exactly n users are transmitting simultaneously. (Hint: Use the binomial distribution) (d) (4 pts.) Find the probability that there are greater than 20 users transmitting simultaneously. (e) (3 pts.) On average how many users are active simultaneously? (f) (3 pts.) If each user transmits at 10 percent of the time. Will the answer in part (d) increase or decrease? Why