Calculating Investment Appraisal with Inflation rates

I don’t know how to calculate Inflated prices when the selling price per unit are different each year. For instance:

Year 1- SP=$15/unit
Year 2- SP=$18/unit
Year 3- SP=$22/unit
Year 4- SP=$22/unit

Selling price inflation is 4% per year

P.S: I know how to calculate Inflated prices when the prices are the same. Different prices are a confusion.

Please Slove this for me?