Original study example
A model gives total cost C(x) = 120 + 8x. Find C(15), then explain the fixed and variable parts without treating this example as your course outline.
Work through the example
C(15) = 120 + 120 = 240. The fixed cost is 120; each extra unit adds 8. Check C(0) = 120 and C(16) - C(15) = 8. Bring a problem from your actual chapter to decide which methods to work on next.