In CSMA/CD, after the fifth collision, what is the probability that a node chooses K=4? The result K=4 corresponds to a delay of how many seconds on a 10Mbps Ethernet? How many collisions are at least required for K = 4 to become possible? Please work out the probability of choosing K = 4 for the smallest number of collisions such that K = 4 is possible, the next larger number of collisions, and so on, until the 7th collision.