[SysTaMatIcS]

10 minutes , easy .
First the cop and the thief , then take the cop back , leave the thief on the other side .
then take the cop and a girl , come back with the cop and the thief.
then take the mother and the girl , come back with the mom.
then take it with the mother and the father , drop the mom off and come back with the father only.
take the cop with the thief and come back with the father only , take a boy and go drop him off.
then come back with the cop and the thief , take the last boy , drop him and go back and take the thief.