What is the maximum miles per gallon of the car with 8 cylinders or produced before 1980?
return cars ;return #1 with  8 cylinders ;return #1 produced before 1980 ;return #2 ,  #3 ;return miles per gallon of #4 ;return the  maximum of #5
['select', 'filter', 'filter', 'union', 'project', 'aggregate']