Answer:
a)
b) 
c) 
d) 
Step-by-step explanation:
Let X the random variable that represent the number of material anomalies occurring in a particular region of an aircraft gas-turbine disk. We know that
The probability mass function for the random variable is given by:
And f(x)=0 for other case.
For this distribution the expected value is the same parameter
,
, 
a. Compute both P(X≤4) and P(X<4).
Using the pmf we can find the individual probabilities like this:




b. Compute P(4≤X≤ 8).







c. Compute P(8≤ X).


d. What is the probability that the number of anomalies exceeds its mean value by no more than one standard deviation?
The mean is 4 and the deviation is 2, so we want this probability




