Cryptology - Compare the amount of work the cryptanalyst is likely to require - Single vs. Double rotation "Suppose a cryptanalyst suspects that
SECEC SYHRI IRFET SSETE INLST AFNIA FSOAI HFSRT TEATE
was obtained by a succession of two rotations with different block lengths and rotation amounts. Compare the amount of work the cryptanalyst is likely to require under this assumption with what she is likely to require under the assumption of a single rotation. Try to do the cryptanalyst’s work."
I am totally lost here regarding what they mean by "compare the work" and what a succession of two rotations entails. The book is very poorly written with lots of mistakes and just asked this question randomly without any mention of any such thing in the chapter. Any help is greatly appreciated!
 A: One of the naive methods of encryption is to divide text into a few blocks of equal length, and to rotate letters inside each block.
Example:
Text : HELLOMYNEWWORLD (HELLO, MY NEW WORLD).
(We will ignore spaces, dots, etc)
Block length can be $3$, $5$ or $15$ (factors of $15$ - length of text).
Suppose Block length is $5$. Let rotation amount is $2$.
We'll denote this operation as $R(5,2)$.
Then we'll get 
1) HELLO MYNEW WORLD
2) LOHEL EWMYN LDWOR
3) LOHELEWMYNLDWOR
To make encryption more complicated, 
let's apply rotation for other block length (suppose for $3$).
Let rotation amount is $1$. 
We'll denote this rotation as $R(3,1)$:
4) LOH ELE WMY NLD WOR
5) HLO EEL YWM DNL RWO
6) HLOEELYWMDNLRWO
So, applying sequentially $R(5,2), R(3,1)$, we get cipher text HLOEELYWMDNLRWO.
To decrypt, we need to apply inverse rotations in inverse order:
A) rotation R(3,2) as complementary/inverse rotation for R(3,1); (why?)
B) rotation R(5,3) as complementary/inverse rotation for R(5,2).

Your task:
When apply rotation $R(5,3)$ first, and rotation $R(3,2)$ after, we'll get:
1) SECEC SYHRI IRFET SSETE INLST AFNIA FSOAI HFSRT TEATE
2) ECSEC RISYH ETIRF TESSE STINL IAAFN AIFSO RTHFS TETEA
3) ECSECRISYHETIRFTESSESTINLIAAFNAIFSORTHFSTETEA
4) ECS ECR ISY HET IRF TES SES TIN LIA AFN AIF SOR THF STE TEA
5) SEC REC YIS THE FIR STE SSE NTI ALI NAF FAI RSO FTH EST ATE
6) SECRECYISTHEFIRSTESSENTIALINAFFAIRSOFTHESTATE
Can you read this???

To compare amount of work, you need to find factors of $45$ (text length): $3,5,9,15,45$.
If there was applied $1$ rotation, then amount of work is:
1) to check block length $3$ and amounts of rotation $1,2$;
2) to check block length $5$ and amounts of rotation $1,2,3,4$;
3) to check block length $9$ and amounts of rotation $1,2,...,8$;
4) to check block length $15$ and amounts of rotation $1,2,...,14$;
5) to check block length $45$ and amounts of rotation $1,2,...,44$.
Total amount of work is $2+4+8+14+44$ items.
If there were applied $2$ rotations, then amount of work is to check each pair of block lengths with their possible amounts of rotations.
Note, that rotations $R(15,2),R(3,1)$ and $R(3,1),R(15,2)$ are different rotations.
