Hello tutors can I please get support with the following statistics problem?

The time in hours required to repair a machine is an exponentially distributed random variable with expected value of two hours. How would you use the formula for the exponential density functionf(x)= ee,x0 to find :

a. The probability that a repair time exceeds two hours?

b. A company has four machines that need repairs. What is the probability that two of them require less than two hours to be repaired?

c. If repairing a machine has already taken two hours and the repair person is not done, what is the probability that it will take 3 or more hours to repair the machine?