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) if it is an average of 3 counts per minute, find the value of such that . (round yours answers to 4 decimal places.)