(a) A ten-digit phone number in the US consists of a three-digit area code followed by a three-digit exchange followed by a four digit number. (i) The first digit of the area code cannot be 0 or 1. The first digit of the exchange cannot be 0 or 1. How many different ten-digit phone numbers can be formed? (ii) Can a city with 2 million telephone numbers use the same area code? Why or why not?