How many more hybrid electric vehicles was EnviroCAB authorized to have than existing companies?
return EnviroCAB ;return existing companies ;return hybrid electric vehicles authorized to have of #1 ;return hybrid electric vehicles authorized to have of #2 ;return number of #3 ;return number of #4 ;return the difference of #5 and #6
['select', 'select', 'project', 'project', 'aggregate', 'aggregate', 'arithmetic']