∵ 100× 13= 1300< 1392,

∴ The number of people in Group B is not less than 50 and not more than100;

(2) Form two tour groups, A and B, with X and Y people respectively.

Then13x+11y =1392.

9(x+y)= 1080。

Solution: x=36

y=84。

Or13x+11y =1392.

1 1(x+y)= 1080。

The solution is x= 156.

Y=-636/ 1 1 (irrelevant, omitted)

A: There are 36 and 84 tour groups A and B respectively.