Let x_1, x_2, x_3, x_4 be in a geometric progression. If 2, 7, 9, 5 are subtracted respectively from x_1, x_2, x_3, x_4, then the resulting numbers…

Let $\displaystyle x_1, x_2, x_3, x_4$ be in a geometric progression. If $\displaystyle 2$, $\displaystyle 7$, $\displaystyle 9$, $\displaystyle 5$ are subtracted respectively from $\displaystyle x_1, x_2, x_3, x_4$, then the resulting numbers are in an arithmetic progression. Then the value of $\displaystyle \frac{1}{24}\left(x_1 x_2 x_3 x_4\right)$ is: