two pharmaceutical companies have both discovered similar vaccines to prevent the spread of covid-19 (hooray!). while gd pharma's vaccine sells at $100 per unit, biothink sells its vaccine at $90 per unit. this price differential has been mainly attributed to the companies' different capital financing decisions. biothink used its retained earnings to develop their vaccine, while gd pharma borrowed funds from banks to develop their vaccine. simply put, gd pharma pays a higher interest on its capital, which makes it necessary to price its vaccine higher. thus, the key driver for biothink's competitive advantage is . a. availability of complements b. economies of scale c. low-cost input factors d. superior customer service