Assume that $x$ and $y$ represent positive real numbers. Using the distributive property to help simplify the expression $$2 \sqrt{9 xy}-\sqrt{16 xy}+ 3 \sqrt{49 xy}$$ into the simplest radical form $A \sqrt{C}$, where $A$ and $C$ are either integers or monomials.

Answer: $A =$ and $C =$

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