Product of a geometric collection from it is center term

If the $5$ - th regard to the G.P is its center term and also its value is 2, after that locate the item of all regards to this General Practitioner?

My strategy :

Since $a_5$ is the center term, so the General Practitioner has 9 terms.

$$P_9 = a\cdot ar\cdot ar^2 \cdot ar^3 \cdot 2\cdot ar^5 \cdots ar^8$$

which leaves us $P_9 = 2\cdot (ar^4)^8$ ... I am not obtaining just how to continue better? Is this strategy also deal with?