Probibility of error

I havent been able to figure out how to do any of this....


Here is my problem:

A scale is designed so that when items are weighted, the errors indicate weights are normally distributed with a mean of 0g and a standard deviation of 1g. If an item is randomly selected and weighed, what is the probability that it has a error between -0.5g and 0.5g?

Please show one problem you have been able to solve.

Do you have an empirical rule? That might produce a good 1st approximation.