Graph the Integrand and Use Areas to Evaluate the Integral $$\int _ { - 3 } ^ { 3 } ( 2 x + 6 ) d x$$

Graph the integrand and use areas to evaluate the integral.
- $$\int _ { - 3 } ^ { 3 } ( 2 x + 6 ) d x$$

A) 12
B) 36
C) 18
D) 72