A SysOps administrator manages a steady baseline of compute that currently runs on m5.large On-Demand instances across two Regions. The team plans to migrate some workloads to c6i instances and a portion to AWS Fargate over the next year, but they want to commit now to reduce costs on their consistent baseline usage. They need the maximum discount while retaining the flexibility to change instance families, sizes, and even Regions without losing the committed discount. Which purchasing option best meets these requirements?