For every dollar increase in the price of music cds sold by a record label, the demand for the cds drops by 100. however, 4,000 cds have already been preordered. if x is the price of a cd, which statement is true about the revenue, r, of the record label? a. the equation r = -100x2 + 4,000x can be used to find that the maximum revenue earned by the record label from cd sales is $10,000. b. the equation r = -100x2 + 4,000x can be used to find that the maximum revenue earned by the record label from cd sales is $40,000. c. the equation r = -4,000x2 + 100x can be used to find that the maximum revenue earned by the record label from cd sales is $10,000. d. the equation r = -4,000x2 + 100x can be used to find that the maximum revenue earned by the record label from cd sales is $40,000.