In Problems $2732,$ find the indicated derivative. Assume that all vector functions are differentiable. $27.$ d dt $[$r$($t$)$ r $($t$)]28.$ d dt $[$r$($t$)($t r$($t$))]29.$ d dt $[$r$($t$)($r $($t$)$ r $($t$))]30.$ d dt $[$r$1($t$)($r$2($t$)$ r$3($t$))]31.$ d dt cr$1(2$t$)$ r$2$ a $1$ t b d $32.$ d dt ft $3$ r$($t $2)$g