Sorry, I just realized that the page 159 isn't on google books, so here's the problem in full:

"Exercise12: (a) show that if A is a set of ordinals that contains a largest elementalphathen UA is less than or equal toalpha.

(b) give examples of A andalphaas in point (a) such that:

(b1) UA =alpha

(b2) UA is strictly less thanalpha"

And it's b2 that I'm having trouble with.

Again, any help would be great.

Regards

Sam