"Given the company’s performance record and based on the empirical rule of normal distribution (also known as the 68%-95%-99.7% rule), what would be the

**lower**bound of the range of sales values that contains 68% of the monthly sales?"

Here is the key data from the sheet, which have all be confirmed as correct:

Median 8124.23

Mean 8235.78

Std Dev 780.93

I've tried taking the mean and subtracting 1 Std Dev giving me 7343.30 which was wrong. I tried using a function in excel Norm.Inv with a .34 probability which gave me

7913.68 which was also wrong. If you need the full sheet I can attach it. Thanks in advance.