Hi alanforde800Maximus,

We're told that for each order, a certain company charges a delivery fee D that depends on the total price X of the merchandise in the order, where D and X are in dollars and
D = 3, if 0 < X <= 100
D = 3 + (X-100)/100, if 100 < X <= 500
D = 7, if X > 500
and George placed two separate orders with the company. We're asked if the total price of the merchandise in the two orders greater than $499. This is a YES/NO question and can be solved by TESTing VALUES. It's worth noting that - based on the 'pay scale' - the 'second level' fee would be between $3 and $7, inclusive (depending on the value of X).

1) The delivery fee for one of the two orders was $3.

Fact 1 tells us about just 1 of the 2 orders. With a fee of $3, we know that that first order cost between $0 and $100. However, we don't know anything about what the 2nd order cost.
IF... the 2nd fee was $3, then the total cost would be no more than $200 and the answer to the question would be NO.
IF... the 2nd fee was $7, then the total cost would be at least $500 and the answer to the question would be YES.
Fact 1 is INSUFFICIENT.

2) The sum of the delivery fees for the two orders was $10.

IF the two individual fees were $3 and $7, then the total cost would be at least $500 (since the $7 charge occurs when X is $500 or more) and the answer would be YES.

We do have to consider the possibility that both fees were from the 'second level'....
When
X=200, the fee is (3 + 1) = $4
X=250, the fee is (3 + 1.50) = $4.50
X=300, the fee is (3 + 2) = $5
X=400, the fee is (3 + 3) = $6
Etc.

With a total fee of $10, the total cost of the order will ALWAYS be at least $600 (you can pair any two values and the sum will always be at least that high), so the answer to the question WOULD be YES. In all possible situations, the answer to the question is YES.
Fact 2 is SUFFICIENT.

Final Answer: B

GMAT assassins aren't born, they're made,
Rich