The random variable X$,$ representing the num$-$b er of errors p er $100$ lines of software co de$,$ has the

following probability distribution:

x $23456$

f $($x$)0\mathrm{.}010\mathrm{.}250\mathrm{.}40\mathrm{.}30\mathrm{.}04$

Using Theorem $4\mathrm{.}2$ on page $121,$nd the variance of

X$.$