A new operating system for smart$-$phones that makes visiting social networking sites easier attracts new smart$-$phone users. At the same time new firms enter the smart$-$phone market. We can conclude that: A new operating system for smart$-$phones that makes visiting social networking sites easier attracts new smart$-$phone users. At the same time new firms enter the smart$-$phone market. We can conclude that: the price of smart$-$phones will increase. the price of smart$-$phones will decrease. the number of smart$-$phone users will decrease. the number of smart$-$phone users will increase.