Hi everyone,
I need help with calculating the average fleet age. I have a number of cars for the years 2007-2016, and they are included in the age groups of cars less than 2 years, 2-5 years, 5-10 years and 10-20 years. I need an average age for every one year. Thank you in advance for your help.

I attach a data file.
average age of fleet.xlsx