Please answer step by step, applying normal distribution formulas, the previous answer you provided me was incomplete. I

[answerhappygod]

Please answer step by step, applying normal distribution
formulas, the previous answer you provided me was incomplete. I
need calculations and formulas.
The mean of a normal probability distribution is 500; the
standard deviation is 10.
. About 68% of the observations lie between what pair of
values?
a. About 95% of the observations lie between what pair of
values?
b. Almost all of the observations lie between what pair of
values?