tray 12 b to rotate counterclockwise to stash the input paper tray 11 c back into the machine 20 and fold the output paper tray 12 c against the machine 20 the user has to push the input paper tray 11 b to slide it back into the machine along the sliding track 21 which will automatically push the first linkage 132 c and second linkage 133 b to rotate the output paper tray 12 c clockwise so that the output paper tray 12 c is folded against the machine 20 nevertheless instead of pulling pushing the input paper tray 11 c the user can also rotate the output paper tray 12 c counterclockwise clockwise to slide out slide in and unfold fold both paper trays at the same time respectively referring to fig4 in the fourth embodiment of this invention as shown the input paper tray 11 d is the same as in the second embodiment while the output paper tray 12 d is the same as in the third embodiment both paper trays are pivotally attached to the machine 20 at the rear end and near the bottom respectively the input paper tray 11 d and output paper tray 12 d are linked by an interconnecting mechanism 13 d inside the machine 20 the interconnecting mechanism 13 d consists of a first linkage 132 d and a second linkage 133 d the first linkage 132 d is fixed with the input paper tray 11 d at one end while the other end is pivotally pinned to one end of the second linkage 133 d the other.