20. 假設函數 \( f(x,y) = e^{xy} \)，若 \( D \) 為由直線 \( y=x \)，\( y=3x \) 及 \( y=5x-4 \) 所圍成的區域，則 \( \iint_{D} f(x,y)dydx \) 之積分值與下列何選項之積分值相等？
(A) \( \int_{0}^{1} \int_{x}^{5x-4} f(x,y)dydx + \int_{1}^{2} \int_{x}^{3x} f(x,y)dydx \)
(B) \( \int_{0}^{1} \int_{x}^{3x} f(x,y)dydx + \int_{1}^{2} \int_{x}^{5x-4} f(x,y)dydx \)
(C) \( \int_{0}^{1} \int_{x}^{3x} f(x,y)dydx + \int_{1}^{2} \int_{5x-4}^{3x} f(x,y)dydx \)
(D) \( \int_{0}^{1} \int_{x}^{5x-4} f(x,y)dydx + \int_{1}^{2} \int_{5x-4}^{3x} f(x,y)dydx \)