Question types in Hartle's General Relativity?

[TonyS]

I've been leafing through a recently bought copy of James B Hartle's Introduction to Einstein's General Relativity and I notice that some of the questions have one or more letters assigned to them, such as A, B, C, S, P.
It seems that my Pearson New International Edition does not contain the key to these abbreviations, so I'm wondering if anyone has an edition that includes the key and can enlighten me !
Thanks in advance.

 

[George Jones]

In my edition, this key is in the Organizational Notes on page xxii, which is the page that precedes page1.

A = more algebra than most problems
B = problem refers to a Box discussion
C = more challenging than most problems
E = order of magnitude estimate
N = requires computer work
P = requires physics outside of presumed prerequisites
S = straightforward (in Hartle's opinion)

 

[TonyS]

In my edition, this key is in the Organizational Notes on page xxii, which is the page that precedes page1

Thank you for the information

I double checked and my edition only contains the table of contents, the 24 chapters and an index, everything else has been stripped out.
Thanks again.