The numbers 1,6,8,13,15,20 can be placed in the circle below, each exactly once, so that the sum of each pair of numbers adjacent in the circle is a multiple of seven in fact, there is more than one way to arrange the numbers in such a way in the circle. Determine all different arrangments. Note that we will consider two arrangments to be the same if one can be obtained from the other by a series of reflections and rotations