There are twelve ways of arranging the boxes without considering the
pictures. If the thirty pictures were all different the answer would be
93,312. But the necessary deductions for cases where changes of boxes may
be made without affecting the order of pictures amount to 1,728, and the
boxes may therefore be arranged, in accordance with the conditions, in
91,584 different ways. I will leave my readers to discover for themselves
how the figures are to be arrived at.