Answer:
0.4968 = 49.68% probability that the repair time takes between 2 to 4 hours
Explanation:
Exponential distribution:
The exponential probability distribution, with mean m, is described by the following equation:

In which
is the decay parameter.
The probability that x is lower or equal to a is given by:

Which has the following solution:

The probability of finding a value higher than x is:

Average repair time of 2 hours
This means that

What is the probability that the repair time takes between 2 to 4 hours
More than 2:

Less than 4:

Between two and four:

0.4968 = 49.68% probability that the repair time takes between 2 to 4 hours