Which expression is equivalent to startfraction rootindex 4 startroot 6 endroot over rootindex 3 startroot 2 endroot? startfraction rootindex 12 startroot 27 endroot over 2 endfraction startfraction rootindex 4 startroot 24 endroot over 2 endfraction startfraction rootindex 12 startroot 55296 endroot over 2 endfraction startfraction rootindex 12 startroot 177147 endroot over 3 endfraction