The chocolate chip cookies that are produced at Perry’s Cookie Emporium have weights which are approximately normally distributed with the mean weight 180 grams and with standard deviations 20 grams....

The chocolate chip cookies that are produced at Perry’s Cookie Emporium have weights which are approximately normally distributed with the mean weight 180 grams and with standard deviations 20 grams. The cookies, however, are sold by count, not by weight. Perry wants to improve his image, so he decides to set aside lightest 20% of the cookies to be packaged and sold separately. What cookie weight will divide the lightest 20% from the heaviest 80%?