question: A list of the top 10 countries by average invoice size. List country name and average invoice size.
#1 return countries 
#2 return invoice sizes of #1 
#3 return the  average of #2 for each #1 
#4 return the  top 10 highest of #3 
#5 return #1 where #3 is equal to any of #4 
#6 return names of #5 
#7 return #6 ,  #4