Suppose that the log-ons to a computer network follow a Poisson process with an average of 4 counts per minute. (a) What is the mean time between counts (in minutes)? (Round yours answers to 3 decimal places.) (b) What is the standard deviation between counts (in minutes)? (Round yours answers to 3 decimal places.) (c) Let denote the time between two counts. If it is an average of 3 counts per minute, find the value of such that . (Round yours answers to 4 decimal places.)