Functions

If the domain of the function

$f(x) = \sqrt{\log_{(0.6)} (\left| \frac{2x-5}{x^2-4} \right|)}$ is $(-\infty, a] \cup \{b\} \cup [c, d) \cup (e, \infty)$, then the value of $a + b + c + d + e$ is ________.