Evaluate the Integral $$\int _ { 0 } ^ { 8 \pi } \int _ { 0 } ^ { 13 \pi } ( \sin x + \cos y ) d x d y$$

Multiple Choice

Evaluate the integral.
- $$\int _ { 0 } ^ { 8 \pi } \int _ { 0 } ^ { 13 \pi } ( \sin x + \cos y ) d x d y$$

A) $17 \pi$
B) $16 \pi$
C) $9 \pi$
D) $8 \pi$