A business received an offer from an exporter for 20,000 units of product at $15 per unit. The acceptance of the offer will not affect normal production or domestic sales prices. The following data are available: Domestic unit sales price $21 unit manufacturing costs variable 12 fixed 5 What is the differential revenue from the acceptance of the offer? a. $240,000 b. $420,000 c. $300,000 d. $120,000