Answer
See below
Work Step by Step
The mean, median, mode, range, and standard deviation of the data set when the outlier is included:
$\bar x=\frac{120+130+150+180+230+280+320+320+350}{9}=231.1\\ Median =230\\Mode =320\\Range=350-120=230\\\sigma =84.39$
After promotion, the prices are equal to 80% of the initial price.
New mean: $231.1 \times 0.8=184.8$
New median: $230 \times 0.8=184$
New mode: $320 \times 0.8=256$
New range: $230 \times 0.8=184$
New standard deviation: $84.39 \times 0.8=67.512$
