\textbf{If you times some number to the data set,~ the mean or median needs to be times with the same number. So for here, everything times with 0.8.} 
\textbf{A stationery store owner calculated the mean and median price of all types of pen: 5 and 3, respectively. He plans to have a 20\% off sale. What are the new mean and median of pens in that store?} 

(a) \textbf{mean: 4; median: 2.4} 
(b) \textbf{mean: 5; median: 2.4} 
(c) \textbf{~mean: 4; median: 3} 
(d) \textbf{~mean: 5; median: 3} 
(e) \textbf{mean: 2.4; median: 4} 