There is a relationship between confidence interval and standard deviation:

Where

is the mean,

is standard deviation, and n is number of data points.
Every confidence interval has associated z value. This can be found online.
We need to find the standard deviation first:

When we do all the calculations we find that:

Now we can find confidence intervals:

We can see that as confidence interval increases so does the error margin. Z values accociated with each confidence intreval also get bigger as confidence interval increases.
Here is the link to the spreadsheet with standard deviation calculation:
https://docs.google.com/spreadsheets/d/1pnsJIrM_lmQKAGRJvduiHzjg9mYvLgpsCqCoGYvR5Us/edit?usp=sharing
Answer:
I cant help unless i have workable units (0.5) is not a point
but im guessing that you were trying to say (0,5) in which case its
7.07106781187
its a triangle
5 on one side
5 on the other
solve for the hypotenuse
hypotenuse = 
hypotenuse = 7.07106781187
I hope this helps!
The 30% off is $82.50 cheaper. Which would be $192.50