บทสนทานาต่อไปนี้ใช้ตอบคำถามข้อ31-35

KidZania is a nation just for kids. In other words, it is an educational and entertainment Family theme park that allows children to role-play adult activities in a replica city with a functioning economy. At KidZania, children can enjoy playing the role of a number of careers, including a journalist, teacher, flight attendant, pilot, doctor, singer, and banker.

    And of course, when they work, they earn. This edutainment nation has an official currency called KidZos. If children choose to work as a journalist, for example, they will be given a training session before going out from their news station to cover newsworthy events that happen within KidZania. Then they come back to write a story which will be published in the replica city's newspaper. Similarly, if they choose to be a flight attendant, a technician, a nurse or any other job, they will be provided with on-the-job training before being allowed to work in their respective role.

    The KidZOs they earn can be spent on goods and services in the city. And if kids earn a lot, they can save their "money" and earn interest in the KidZania bank. ATM machines are available in the center for them to make withdrawals from their bank accounts. By this means, children learn the value of money. They are prepared for the real world and realize that if they want to have something, they have to work hard for it.

Which of the following is closest in meaning to “interest” (paragraph 3)?