A company has a website that runs on four Amazon EC2 instances that are behind an Application Load Balancer (ALB). When the ALB detects that an EC2 instance is no longer available, an Amazon CloudWatch alarm enters the ALARM state. A member of the company's operations team then manually adds a new EC2 instance behind the ALB. A solutions architect needs to design a highly available solution that automatically handles the replacement of EC2 instances. The company needs to minimize downtime during the switch to the new solution. Which set of steps should the solutions architect take to meet these requirements?