923 - Logical Reasoning

Question: To entice customers away from competitors, Red Label supermarkets have begun offering discounts on home appliances to customers who spend $50 or more on any shopping trip to Red Label. Red Label executives claim that the discount program has been a huge success, since cash register receipts of $50 or more are up thirty percent since the beginning of the program. Which of the following, if true, most seriously weakens the claim of the Red Label executives?

1. Most people who switched to Red Label after the program began spend more than $50 each time they shop at Red Label.
2. Most people whose average grocery bill is less than $50 would not be persuaded to spend more by any discount program.
3. Most people who received discounts on home appliances through Red Label's program will shop at Red Label after the program ends.
4. Since the beginning of the discount program, most of the people who spend $50 or more at Red Label are people who have never before shopped there and whose average grocery bill has always been higher than $50.
5. Almost all of the people who have begun spending $50 or more at Red Label since the discount program began are longtime customers who have increased the average amount of their shopping bills by making fewer trips.