Answer:
0.1353 = 13.53% probability that the lifetime exceeds the mean time by more than 1 standard deviations
Step-by-step 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:

The mean time for the component failure is 2500 hours.
This means that 
What is the probability that the lifetime exceeds the mean time by more than 1 standard deviations?
The standard deviation of the exponential distribution is the same as the mean, so this is P(X > 5000).

0.1353 = 13.53% probability that the lifetime exceeds the mean time by more than 1 standard deviations
We can use pythagorean theorem:
a^2 + b^2 = c^2
4 + 9 = c^2
13 = c^2
sqrt of 13 = c
Hope this helps!
Answer:
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The answer is -- A. Exactly one solution