How many months after the aircraft were delivered to RAF were they test flown at Cunliffe-Owen Aircraft Swaythling?
return the  aircraft were delivered to RAF ;return the  aircraft were test flown at Cunliffe-Owen Aircraft Swaythling ;return month of #1 ;return month of #2 ;return the  difference of #4 and  #3
['select', 'select', 'project', 'project', 'arithmetic']