The set of values of $\mathrm{x}$ satisfying the inequality $|\mathrm{x}-1|+|\mathrm{x}-2| \geq 6$ is
(a) $\left(-\infty, \frac{-3}{2}\right] \cup\left[\frac{9}{2}, \infty\right)$
(b) $\left(\frac{-3}{2}, \frac{9}{2}\right)$
(c) $\left(-\infty, \frac{3}{2}\right]$
(d) $(1,2)$