听力原文： Good morning, everybody. Now I'm going to tell you how to buy a ticket for the BART system. Each person must have a ticket. Children aged not more than four do not need a ticket. Since each of you has a brochure in hand, you may first check the fare chart on the facing page for your destination and cost of your trip. Fare charts show the cost of a one-way trip, multiply by two for a round trip. Then go to a ticket machine and purchase your ticket. Some machines provide change. Others do not. Signs on the machines indicate which ones give change. No machines will give you more than $4.95 in change. Ticket machines will accept nickels, dimes, quarters, $1, $5, $10, and $20 bills. (Note: if your bill is not accepted, turn it upside down and try again.) Machines sell tickets for any amount from a minimum of $1 to a maximum of $40, so you can purchase a ticket good for several rides. Lastly, take your ticket and insert it in the fare gate. The ticket will be returned to you. You must use the same ticket when exiting at your destination. Again, change machines for coins and $1 bills are located in all stations. You can add value to your ticket up to a maximum new total of $40 if there is $7.95 or less remaining. Put the ticket in the 'old ticket' slot and add at least 5 cents or more. You will then get a new ticket combining the old value and the added money. What kind of people don't need a ticket?