6 People arrive randomly and independently at the elevator in a block of flats at an average rate of 4 people every 5 minutes.
- Find the probability that exactly two people arrive in a 1-minute period.
- Find the probability that nobody arrives in a 15 -second period.
- The probability that at least one person arrives in the next \(t\) minutes is 0.9 . Find the value of \(t\).