List the customers first and last name of 10 least expensive invoices.
return invoices ;return how expensive are #1 ;return the  10 lowest of #2 ;return #1 where #2 is equal to any of #3 ;return customers of #4 ;return first names of #5 ;return last names of #5 ;return #6 ,  #7
['select', 'project', 'aggregate', 'comparative', 'project', 'project', 'project', 'union']