Nick, who is a car mechanic, receives damaged cars for repair at a rate of three cars every two hours. He has estimated that, among the cars arriving 75% are minor repairs, which he can fix by himself, while the rest should be sent to the central repair store. Find the probability that there will be at least two cars needing a major repair between 8:00 a.m. and 11:30 a.m. on a particular day.