What was the question for this implicit rationale, and corresponding answer?
Originally the car parts would be a total of 80 * 7 = 560 dollars. Clark got a discount for 560 - 439 = 121 dollars.
 The answer: 121
The question: An auto shop has a part that Clark needs for $80. Clark buys 7 of them and got a discount. If Clark only had to pay $439, how much was the discount?