I did not get the GMAT pattern. Sometimes they say that in inference type question select 'YES' if we can infer about it from the info either 100% correct or 100% wrong. And when we are not sure what will be the answer then only we have to mark NO bcz we can't infer.
So in the 1- a part we are sure that the median is not 20.40 which is wrong 100% so we are sure that we can infer it so it should be YES i have seen other questions where this logic has been used tell me where i am missing the point why there are different rules for different question
NO, NO, NO and $39.001. Consider each of the following statements. Does the information in the three sources support the inference as stated?(A) The median retail cost of the product line is $20.40.Retail Cost = {17, 25, 34, 45, 100}
Median = $34
ANSWER: NO(B) Loyal members who purchase online save more than 50% off the cost of their total purchases and shipping compared to nonmembers."40% off the retail price of all purchases" is mentioned under "Membership benefit sales flyer".
So Loyal members only save 40% and NOT 50%.
ANSWER: NO(C) The minimum purchase amount within the 6-month introductory period is less than the $50.00 charge issued to accounts that are canceled early.Membership contract said "I understand that I will be required to purchase a minimum of one product per month for the first 6 months of membership."
Let's take cheapest item from catalogue: Detox Tea (PS: You should try this, its good

)
Detox tea cost $10.20, i have to buy this each month for 6 months, total amount = 10.2x6 = $61.2 (which is greater than $50)
ANSWER: NO2. If the information contained in all three sources is correct, the member price of an item that retails for $65.00 will be closest to:65(60/100) = $39
ANSWER: $39.00