
Answer :
Referring to the
original diagram, the four stamps
may be given in the shape 1, 2, 3, 4, in three ways;
in the shape 1, 2, 5, 6, in six ways;
in the shape 1, 2, 3, 5, or 1, 2, 3, 7, or 1, 5, 6, 7, or 3, 5, 6, 7,
in twentyeight ways;
in shape 1, 2, 3, 6, or 2, 5, 6, 7, in fourteen ways;
in shape 1, 2, 6, 7, or 2, 3, 5, 6, or 1, 5, 6, 10, or 2, 5, 6, 9, in
fourteen ways.
Thus there are sixtyfive
ways in all.
