Beginners question: Factorised expression, not sure how book got the answer

Question

I have an expression:

$2a^3 / 3a^2 * 6a^5$

and my book gives the answer:

$4a^6$

I get where the $a^6$ is from but how is the $4$ worked out?

Answer 1

Because its $2\cdot6/3 = 12/3=4$. That's without the $a$'s and its exponents.