Chapter 7, page 56

1. a, b; a, c; a, d; a, e; b, c; b, d; b, e; c, d; c, e; d, e.

3. a, b; b, a; a, c; c, a; a, d; d, a; a, e; e, a; b, c; c, b; b, d; d, b; b, e; e, b; c, d; d, c; c, e; e, c; d, e; e, d.

5. 7,920.

7. 30.

9. 

11. -1,201,200.

17. 3¹⁰⁰.

19. 1,2,3,4;     2,1,4,3;     3,1,2,4;     4,1,3,2;
    1,3,4,2;     2,4,3,1;     3,2,4,1;     4,3,2,1;
    1,4,2,3;     2,3,1,4;     3,4,1,2;     4,2,1,3.

Wednesday, May 13, 1998