GMAT Prep Question help needed : Tomo is my exam

total 90 copies on 7 days
let m = #sold on monday
t on tuesday
w on wednesday
th on thursday
f on friday
s on saturday.
su on sunday
s is the highest. to find if f>11
a)th=8
insufficient.
because we can take f=10 and all other days except saturday to be less than 10 and saturday can go as high as 50 to make total 90
or we can take f=12 and all others except saturday to be less than 12 and saturday can still go as high as possible

b)s=38 (max)
thus m+t+w+th+f+su = 90-38 = 52
if f=11, max value of m+t+w+th+su = 10+9+8+7+6 = 40
or total=51<52
thus f>=11
Sufficient.
IMO B

Hi,
As Cans has a already explained this, I would like to add something less significant in terms of the answer. This could be a typing error by her. In the last step, it was written f>=11. Equality doesn't hold. f should be strictly greater than 11 i.e., f>11.

once again thanks for correction Franenstein.
f>11

But the question says that except for the two days friday and saturday, the number of copies sold is equal and not different. Plzzz... explain..

Please post official answer.

"it sold different numbers of copies on any two of the days." doesn't seem very clear.