Evaluate the following:$\int e^{-3x}\cos^3xdx$

Question

$\begin{array}{1 1} (A) \large\frac{e^{-3x}}{24}\normalsize[\sin 3x+\cos 3x]+\large\frac{3e^{-3x}}{40}\normalsize[\sin x+\cos x]+c. \\ (B) \large\frac{e^{-3x}}{24}\normalsize[\sin x+\cos x]-\large\frac{3e^{-3x}}{40}\normalsize[\sin 3x+\cos 3x]+c. \\ (C) \large\frac{e^{-3x}}{24}\normalsize[\sin 3x-\cos 3x]+\large\frac{3e^{-3x}}{40}\normalsize[\sin x-\cos x]+c. \\(D) \large\frac{e^{-3x}}{24}\normalsize[\sin x+\cos x]+\large\frac{3e^{-3x}}{40}\normalsize[\sin 3x+\cos 3x]+c. \end{array}$