JEE Math Practice Question

Let $$|\cos \theta \cos (60-\theta) \cos (60+\theta)| \leq \frac{1}{8}, \theta \epsilon[0,2 \pi]$$. Then, the sum of all $$\theta \in[0,2 \pi]$$, where $$\cos 3 \theta$$ attains its maximum value, is :

1. A.$$6 \pi$$
2. B.$$9 \pi$$
3. C.$$18 \pi$$
4. D.$$15 \pi$$