Correll Company, which operates a mail-order clothing business, is physically located in State L. This year, the firm shipped $18 million of merchandise to customers in State R. State R imposes a 6 percent sales and use tax on the purchase and consumption of retail goods within the state. 

a. Do State R residents who purchased Correll merchandise owe use tax on their purchases? 

b. If State R could legally require Correll to collect a 6 percent tax on mail-order sales made to residents of the state, how much additional revenue would the state collect? Explain the reasoning behind your answer.