The following are configurations of the revolved differential strip and the axis of revolution in volumes of revolved plane areas. Under which conditions is the method of disks applicable? 1. the differential strip is parallel to the axis of revolution 2. the differential strip is perpendicular to the axis of revolution 3. both ends of the rotated differential strip touches the axis of revolution 4. one of the ends of the rotated differential strip touches the axis of revolution 5. none of the ends of the rotated differential strip touches the axis of revolution O 1 and 5 O 2 and 4 O 1 and 3 O 2 and 5 O 1 and 4