Suppose the time spent by a randomly selected student who uses a terminal connected to a local time-sharing computer facility has a gamma distribution with mean 12 min and variance 36 min. (a) What are the values of a and ? B = (b) What is the probability that a student uses the terminal for at most 18 min? (Round your answer to three decimal places.) (c) What is the probability that a student spends between 15 and 27 min using the terminal? (Round your answer to three decimal places.)