D the terms are three times larger because 5 x 3 = 15
You would need 3 pails of plaster, specifically about 2 pails and a fifth of another but you cant buy a fraction of a pail, so 3 pails are needed.
It shouldn’t be any longer vertically so that should be your answer
D
Because it is one of the parent functions

F ∪ H is defined as the set that consists of all elements belonging to either set F or set H (or both).
F ∩ H is defined as the set composed of all elements that belong to both F and H