How to calculate the sums and averages of certain positions in Excel and LibreOffice?

Question

excel

Greetings
Once upon a time, I knew something about formulas in Excel, but those days are long gone and everything is forgotten.

Given two sheets. On one sheet, the name of the products and their prices (there may be a different number of products), and on the second sheet, in the field of the average price, the average price should be calculated approximately according to the following formula (using the example of watermelons):

• the number of identical product positions is read = 4
  
• the sum of the costs is calculated = 4+5+7+6 = 22
  
• we get the average value of the cost (sum of costs / number of positions) = 5.5
  

Tell me who knows how to make a formula, but for the finished version, it’s generally respectful)