1. A seven-digit phone number in the United States consists of a three-digit exchange followed by a four-digit number:

A). The first digit of the exchange is not allowed to be a zero or a one. How many seven-digit numbers can be formed? Can a city of 2 million people be served by a single area code? B). How many exchanges are needed to serve a city of 80,000 people?

2. Would you rather start with a penny ($0.01) and double your wealth every day or start with a dime ($0.10) and double your wealth every five days? Assume you want to make the most possible money.

3. You can purchase a Ford Focus for $16,500 or lease it for $3000 down and $200 per month. Find a function that describes how the cost of the lease depends on time. How long can you lease the car before you have paid more the purchase price?