8 The number of flaws in a randomly chosen 100 metre length of ribbon is modelled by a Poisson distribution with mean 1.6. The random variable \(X\) metres is the distance between two successive flaws. Show that the distribution function of \(X\) is given by
$$\mathrm { F } ( x ) = \begin{cases} 1 - \mathrm { e } ^ { - 0.016 x } & x \geqslant 0
0 & x < 0 \end{cases}$$
and deduce that \(X\) has a negative exponential distribution, stating its mean.
Find
- the median distance between two successive flaws,
- the probability that there is a distance of at least 50 metres between two successive flaws.