The table below shows recent worldwide market shares of producers of inkjet printers.
Firm Share of Worldwide Market Sales
Brother ........................... 3%
Canon ............................. 17
Dell ................................ 6
Epson .............................. 18
Hewlett-Packard ................. 41
Lexmark ........................... 13
Samsung ........................... 1
Other .............................. 1
a. In this year, what was the four-firm concentration ratio in the inkjet-printer industry?
b. In this year, what was the seven-firm concentration ratio in the inkjet-printer industry?