Find the first name and gpa of the students whose gpa is lower than the average gpa of all students.
return students  ;return gpa  of #1 ;return average of #2 ;return #1 where #2 is lower than #3 ;return first name of #4 ;return gpa  of #4 ;return #5 ,  #6
['select', 'project', 'aggregate', 'comparative', 'project', 'project', 'union']