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Wouldn't part b of this question be correct? It asks for the wavelengths that correspond to the upper and lower. Isn't Violet (with a wavelength of 400 nm) on the upper end?
So the correct answer is for the one on the left and for the one on the right since you are considering the range. In wavelength terms Red is in the upper end, in frequency and therefore energy terms violate is in the upper end.