A company is planning to host its stateful web-based applications on AWS. A SysOps administrator is using an Auto Scaling group of Amazon EC2 instances. The web applications will run 24 hours a day…

A company is planning to host its stateful web-based applications on AWS. A SysOps administrator is using an Auto Scaling group of Amazon EC2 instances. The web applications will run 24 hours a day, 7 days a week throughout the year. The company must be able to change the instance type within the same instance family later in the year based on the traffic and usage patterns. Which EC2 instance purchasing option will meet these requirements MOST cost-effectively?