Evaluate the Integral $$\int \cos 7 x \cos 3 x d x$$

Multiple Choice

Evaluate the integral.
- $$\int \cos 7 x \cos 3 x d x$$

A) $\frac { 1 } { 8 } \sin 4 x - \frac { 1 } { 20 } \sin 10 x + C$
B) $\frac { 1 } { 8 } \cos 4 x + \frac { 1 } { 20 } \cos 10 x + C$
C) $\frac { 1 } { 8 } \sin 7 x + \frac { 1 } { 20 } \sin 3 x + C$
D) $\frac { 1 } { 8 } \sin 4 x + \frac { 1 } { 20 } \sin 10 x + C$