Step-by-step explanation: As mentioned in the question about Mary Lou, she is almost better than others in mostly every field like music, English, math, and also a good employee etc. It is well known that she can provide advantage in many filed
While considering her work at trading area, it requires mostly comparative advantage to perform well than other, which is not an expertise of Mary.
As she cannot persist betterment in every field, she does not have skills required in trading which may lead to increasing her potential by trading something.