SOLUTION: amount being spent on personal phone calls followed a normal distribution with an average of $500/month and a standard eviation of $50/month. What is the probablity that a randomly

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Question 948849: amount being spent on personal phone calls followed a normal distribution with an average of $500/month and a standard eviation of $50/month. What is the probablity that a randomly selected month had a call expense between $375 and $590?

I have come up with an answer of 0.9999 and 0.9579.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
How do you have two answers?
You should only have 1.
Find the z score for both points.
z=%28x-mu%29%2Fsigma
z%5B1%5D=%28375-500%29%2F50=-2.5
z%5B2%5D=%28590-500%29%2F50=1.8
So then,
P=P%28z%5B2%5D%29-P%28z%5B1%5D%29
P=0.96407-0.00621
P=0.95786