Answer:
a)
b)
c)
Step-by-step explanation:
For this case we know that the mean for the random variable of interest is and the variance so then the deviation would be
The z score is given by thsi formula:
Part a
We want this probability:
And if we find the z score we got:
And we can find this probability:
Part b
We want this probability:
And if we find the z score we got:
And we can find this probability:
Part c
We want this probability:
And if we find the z score we got:
And we can find this probability: