Let

f$($x$)=$

$$

$0$if$$x $<0$x$$if$0$ x $12$ x$$if$1<$ x $20$if$$x $>2$

and

g$($x$)=$

xf$($t$)$ dt$\mathrm{.}0$

$($a$)$

Find an expression for

g$($x$)$

similar to the one for

f$($x$)$