How Many Reserved Instances Can the QA Team Use?

Answer - B.

The management account has three reserved instances and two of them are used by Dev department so we have only one reserved instance left that will be used by QA department.

The QA team needs three instances so remaining two instances can be added afterwards.

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The answer is B. One Reserved instance.

Explanation:

When an AWS account is configured for consolidated billing, it enables the payer account to pay for all accounts associated with it. The payer account can also view a combined view of AWS costs for all accounts in the organization. However, this does not mean that the reserved instances purchased by the payer account can be used by all accounts. Reserved instances are specific to the instance type, availability zone, and region for which they were purchased. Therefore, to use the reserved instance, it must match the instance type, availability zone, and region of the running instance.

In this scenario, the management account has purchased three reserved instances. However, the Dev department is currently using two reserved instances, which means there is only one reserved instance left. The QA department is planning to use three EC2 instances, but it does not necessarily mean that all three instances will match the reserved instance purchased by the management account.

Therefore, it is only possible for the QA team to use one reserved instance that matches their requirements. The other two instances will be billed at the On-Demand rate.

Hence, the answer is B. One Reserved instance.