Reading 28 Butterfly spread using put options

CFA Level III
#1

Can someone help explain why the Max Profit is X2 - X1 - (p1 - 2p2 + p3) (Par B in example 7) but not X3 - X2 - (p1 - 2p2 + p3)? Thanks.

#2

Sorry for the confusion. It should be Reading 29 and it is indeed X3 - X2 - (p1 - 2p2 + p3).

#3

I still have question about breakeven. Why first breakeven ST* = X1 + p1 - 2p2 + p3 but not ST* = X3 - (p1 - 2p2 + p3)? Why second breakeven ST* = 2X2 - X1 - p1 + 2p2 - p3 but not ST* = 2X2 - X3 + (p1 - 2p2 + p3)? Thanks.

#4

Yes, It is corrected in errata