What are the maximum, minimum, and average booked count for the products booked?
return products ;return #1 that  are booked ;return booked counts of #2 ;return maximum of #3 ;return minimum of #3 ;return average of #3 ;return #4 ,  #5 ,   #6
['select', 'filter', 'project', 'aggregate', 'aggregate', 'aggregate', 'union']