How to add two different column value and paste in another column?

Hello Experts !

The scenerio is: i need to sum column A and column B and write final value in Column C.
How can i acheive that.
NOTE: formula for this case is : (price - price2)/price2

Here the sample Excel file :
SampleData.xlsx (7.9 KB)

What is exactly needed sum of price and price2 or price-price2/ price2??