Evaluate the Indefinite Integral $\int x \cos 9 x d x$

Multiple Choice

Evaluate the indefinite integral. $\int x \cos 9 x d x$

A) $\frac{1}{81} \sin 9 x+\frac{x}{9} \cos 9 x+C$
B) $\frac{1}{81} \cos 9 x+\frac{x}{9} \sin 9 x+C$
C) $\frac{1}{9} \cos 9 x+\frac{x}{9} \sin 9 x+C$
D) $\frac{x}{81} \cos 9 x+\frac{x}{9} \sin 9 x+C$
E) $\text { None of these }$