In the following figure, rectangle represents Doctors, circle represents Essayists, triangle represents cooks and square represents Europeans. Which set of letters represents Essayists who are not cooks?
The weights of 4 boxes are 30, 70, 60 and 20 kilograms. Which of the following cannot be the total weight, in kilograms, of any combination of these boxes and in a combination a box can be used only once?