3.3.26. Let X denote time until failure of a device and let r(x) denote the hazard
function of X.
(a) If r(x) = cx^b; where c and b are positive constants, show that X has a Weibull
distribution; i.e.,
$$f(x) = \begin{cases}
cx^b \exp\left\{-\frac{cx^{b+1}}{b+1}\right\} & 0 < x < \infty \\
0 & \text{elsewhere}.
\end{cases}$$
(3.3.12)