The function $f$ is continuous for $- 4 \leq x \leq 4$. The graph of $f$ shown above consists of five line segments. What is the average value of $f$ on the interval $- 4 \leq x \leq 4$ ?\\
(A) $\frac { 1 } { 8 }$\\
(B) $\frac { 3 } { 16 }$\\
(C) $\frac { 15 } { 16 }$\\
(D) $\frac { 3 } { 2 }$