The fixed cost of performing densitomete scans is 1,234 monetary units (m.u.) per month. The variable cost of performing 30 scans a day is 2,499 m.u. per month. The total cost of performing 50 scans a day is 4,433 m.u. per month. What is the mean marginal cost of each of the 20 extra scans a day that are done when the number of scans rises from 30 to 50 a day? Select one: O a. 124.4 m.u. O b. More than 80 m.u. O c. 88.7 m.u. O d. Less than 40 m.u